KVM: arm64: Add debug UART hacks at EL2
Provide a standalone mechanism for debug UART access at EL2. It's a
debug hack, so please try not to get too offended by it.
[ qperret: re-map UART at EL2 in protected mode ]
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Quentin Perret <qperret@google.com>
diff --git a/arch/arm64/kernel/image-vars.h b/arch/arm64/kernel/image-vars.h
index 2d4d683..1bb2a3e 100644
--- a/arch/arm64/kernel/image-vars.h
+++ b/arch/arm64/kernel/image-vars.h
@@ -128,6 +128,10 @@
/* pKVM static key */
KVM_NVHE_ALIAS(kvm_protected_mode_initialized);
+#ifdef CONFIG_KVM_ARM_HYP_DEBUG_UART
+KVM_NVHE_ALIAS(kvm_hyp_debug_uart_set_basep);
+#endif
+
#endif /* CONFIG_KVM */
#endif /* __ARM64_KERNEL_IMAGE_VARS_H */
diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig
index 8a5fbbf..7564cd5 100644
--- a/arch/arm64/kvm/Kconfig
+++ b/arch/arm64/kvm/Kconfig
@@ -56,4 +56,12 @@
If unsure, say N.
+config KVM_ARM_HYP_DEBUG_UART
+ bool "Hack up some basic UART functionality at EL2"
+
+config KVM_ARM_HYP_DEBUG_UART_ADDR
+ hex "Physical address of the PL011 for EL2 to use"
+ depends on KVM_ARM_HYP_DEBUG_UART
+ default 0x09000000
+
endif # VIRTUALIZATION
diff --git a/arch/arm64/kvm/hyp/debug-pl011.h b/arch/arm64/kvm/hyp/debug-pl011.h
new file mode 100644
index 0000000..c76108a
--- /dev/null
+++ b/arch/arm64/kvm/hyp/debug-pl011.h
@@ -0,0 +1,227 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Stand-alone header for basic debug output on the PL011 UART. To use it,
+ * ensure that CONFIG_KVM_ARM_HYP_DEBUG_UART is enabled and that
+ * CONFIG_KVM_ARM_HYP_DEBUG_UART_ADDR is the physical address of the PL011
+ * UART that you want to use. Then just include this header and try not to
+ * vomit at the state of the macros and functions it provides.
+ *
+ * The C functions only work when the MMU is enabled, but the assembly macros
+ * should work pretty much everywhere.
+ *
+ * It's slow and racy, but you'll be fine. Patches unwelcome.
+ */
+
+#ifndef __ARM64_KVM_HYP_DEBUG_PL011_H__
+#define __ARM64_KVM_HYP_DEBUG_PL011_H__
+
+#ifdef CONFIG_KVM_ARM_HYP_DEBUG_UART
+
+#define HYP_PL011_BASE_PHYS CONFIG_KVM_ARM_HYP_DEBUG_UART_ADDR
+#define HYP_PL011_UARTFR 0x18
+
+#define HYP_PL011_UARTFR_BUSY 3
+#define HYP_PL011_UARTFR_FULL 5
+
+#ifdef __ASSEMBLY__
+
+.macro hyp_pl011_base, tmp
+ mrs \tmp, sctlr_el2
+ tbz \tmp, #0, 9990f
+ isb
+
+alternative_cb kvm_hyp_debug_uart_set_basep
+ movz \tmp, #0
+ movk \tmp, #0, lsl #16
+ movk \tmp, #0, lsl #32
+ movk \tmp, #0, lsl #48
+alternative_cb_end
+
+ kern_hyp_va \tmp
+ ldr \tmp, [\tmp]
+ b 9991f
+9990: mov \tmp, HYP_PL011_BASE_PHYS
+9991:
+.endm
+
+/*
+ * 'c' is a W register containing the character to transmit. Preserved.
+ * 'tmpnr' is the number of another scratch register. Clobbered.
+ */
+.macro hyp_putc, c, tmpnr
+9992: hyp_pl011_base x\tmpnr
+ ldr w\tmpnr, [x\tmpnr, HYP_PL011_UARTFR]
+ tbnz w\tmpnr, HYP_PL011_UARTFR_FULL, 9992b
+ hyp_pl011_base x\tmpnr
+ str \c, [x\tmpnr]
+9992: hyp_pl011_base x\tmpnr
+ ldr w\tmpnr, [x\tmpnr, HYP_PL011_UARTFR]
+ tbnz w\tmpnr, HYP_PL011_UARTFR_BUSY, 9992b
+.endm
+
+/*
+ * 's' is an X register containing the address of the string to print.
+ * 'tmpnr1' and 'tmpnr2' are numbers of other scratch registers.
+ * All three registers clobbered.
+ *
+ * The string must be mapped, so it's best to use a combination of '.ascii'
+ * and PC-relative addressing (i.e. an ADR instruction)
+ */
+.macro hyp_puts, s, tmpnr1, tmpnr2
+9993: ldrb w\tmpnr1, [\s]
+ cbz w\tmpnr1, 9993f
+ hyp_putc w\tmpnr1, \tmpnr2
+ add \s, \s, #1
+ b 9993b
+9993: mov w\tmpnr1, '\n'
+ hyp_putc w\tmpnr1, \tmpnr2
+.endm
+
+.macro __hyp_putx4, xnr, tmpnr
+ bic x\xnr, x\xnr, #0xfffffff0
+ sub w\tmpnr, w\xnr, #10
+ tbnz w\tmpnr, #31, 9994f
+ add x\xnr, x\xnr, #0x27
+9994: add x\xnr, x\xnr, #0x30
+ hyp_putc w\xnr, \tmpnr
+.endm
+
+/*
+ * 'x' is an X register containing a value to printed in hex. Preserved.
+ * 'tmpnr1' and 'tmpnr2' are numbers of other scratch registers. Clobbered.
+ */
+.macro hyp_putx64, x, tmpnr1, tmpnr2
+ mov w\tmpnr1, '0'
+ hyp_putc w\tmpnr1, \tmpnr2
+ mov w\tmpnr1, 'x'
+ hyp_putc w\tmpnr1, \tmpnr2
+ movz x\tmpnr1, #15, lsl #32
+9995: bfxil x\tmpnr1, \x, #60, #4
+ ror \x, \x, #60
+ __hyp_putx4 \tmpnr1, \tmpnr2
+ ror x\tmpnr1, x\tmpnr1, #32
+ cbz w\tmpnr1, 9995f
+ sub x\tmpnr1, x\tmpnr1, #1
+ ror x\tmpnr1, x\tmpnr1, #32
+ b 9995b
+9995: mov w\tmpnr1, '\n'
+ hyp_putc w\tmpnr1, \tmpnr2
+.endm
+
+#else
+
+static inline void *__hyp_pl011_base(void)
+{
+ unsigned long ioaddr;
+
+ asm volatile(ALTERNATIVE_CB(
+ "movz %0, #0\n"
+ "movk %0, #0, lsl #16\n"
+ "movk %0, #0, lsl #32\n"
+ "movk %0, #0, lsl #48",
+ kvm_hyp_debug_uart_set_basep)
+ : "=r" (ioaddr));
+
+ return *((void **)kern_hyp_va(ioaddr));
+}
+
+static inline unsigned int __hyp_readw(void *ioaddr)
+{
+ unsigned int val;
+ asm volatile("ldr %w0, [%1]" : "=r" (val) : "r" (ioaddr));
+ return val;
+}
+
+static inline void __hyp_writew(unsigned int val, void *ioaddr)
+{
+ asm volatile("str %w0, [%1]" : : "r" (val), "r" (ioaddr));
+}
+
+static inline void hyp_putc(char c)
+{
+ unsigned int val;
+ void *base = __hyp_pl011_base();
+
+ do {
+ val = __hyp_readw(base + HYP_PL011_UARTFR);
+ } while (val & (1U << HYP_PL011_UARTFR_FULL));
+
+ __hyp_writew(c, base);
+
+ do {
+ val = __hyp_readw(base + HYP_PL011_UARTFR);
+ } while (val & (1U << HYP_PL011_UARTFR_BUSY));
+}
+
+/*
+ * Caller needs to ensure string is mapped. If it lives in .rodata, you should
+ * be good as long as we're using PC-relative addressing (probably true).
+ */
+static inline void hyp_puts(char *s)
+{
+ while (*s)
+ hyp_putc(*s++);
+ hyp_putc('\n');
+}
+
+static inline void __hyp_putx4(unsigned int x)
+{
+ x &= 0xf;
+ if (x <= 9)
+ x += '0';
+ else
+ x += ('a' - 0xa);
+ hyp_putc(x);
+}
+
+static inline void __hyp_putx4n(unsigned long x, int n)
+{
+ int i = n >> 2;
+
+ hyp_putc('0');
+ hyp_putc('x');
+
+ while (i--)
+ __hyp_putx4(x >> (4 * i));
+
+ hyp_putc('\n');
+}
+
+static inline void hyp_putx32(unsigned int x)
+{
+ __hyp_putx4n(x, 32);
+}
+
+static inline void hyp_putx64(unsigned long x)
+{
+ __hyp_putx4n(x, 64);
+}
+
+#endif
+
+#else
+
+#warning "Please don't include debug-pl011.h if you're not debugging"
+
+#ifdef __ASSEMBLY__
+
+.macro hyp_putc, c, tmpnr
+.endm
+
+.macro hyp_puts, s, tmpnr1, tmpnr2
+.endm
+
+.macro hyp_putx64, x, tmpnr1, tmpnr2
+.endm
+
+#else
+
+static inline void hyp_putc(char c) { }
+static inline void hyp_puts(char *s) { }
+static inline void hyp_putx32(unsigned int x) { }
+static inline void hyp_putx64(unsigned long x) { }
+
+#endif
+
+#endif /* CONFIG_KVM_ARM_HYP_DEBUG_UART */
+#endif /* __ARM64_KVM_HYP_DEBUG_PL011_H__ */
diff --git a/arch/arm64/kvm/hyp/nvhe/setup.c b/arch/arm64/kvm/hyp/nvhe/setup.c
index 37002b9..47b4895 100644
--- a/arch/arm64/kvm/hyp/nvhe/setup.c
+++ b/arch/arm64/kvm/hyp/nvhe/setup.c
@@ -23,6 +23,25 @@
#define hyp_percpu_size ((unsigned long)__per_cpu_end - \
(unsigned long)__per_cpu_start)
+#ifdef CONFIG_KVM_ARM_HYP_DEBUG_UART
+unsigned long arm64_kvm_hyp_debug_uart_addr;
+static int create_hyp_debug_uart_mapping(void)
+{
+ phys_addr_t base = CONFIG_KVM_ARM_HYP_DEBUG_UART_ADDR;
+ unsigned long haddr;
+
+ haddr = __pkvm_create_private_mapping(base, PAGE_SIZE, PAGE_HYP_DEVICE);
+ if (!haddr)
+ return -1;
+
+ arm64_kvm_hyp_debug_uart_addr = haddr;
+
+ return 0;
+}
+#else
+static int create_hyp_debug_uart_mapping(void) { return 0; }
+#endif
+
static void *vmemmap_base;
static void *shadow_table_base;
static void *hyp_pgt_base;
@@ -132,6 +151,10 @@
if (ret)
return ret;
+ ret = create_hyp_debug_uart_mapping();
+ if (ret)
+ return ret;
+
return 0;
}
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 392ff7b..148b036 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -531,6 +531,44 @@
return ret;
}
+#ifdef CONFIG_KVM_ARM_HYP_DEBUG_UART
+extern unsigned long __kvm_nvhe_arm64_kvm_hyp_debug_uart_addr;
+
+void __init kvm_hyp_debug_uart_set_basep(struct alt_instr *alt,
+ __le32 *origptr, __le32 *updptr,
+ int nr_inst)
+{
+ int i;
+ u64 addr = (u64)kvm_ksym_ref(&__kvm_nvhe_arm64_kvm_hyp_debug_uart_addr);
+
+ BUG_ON(nr_inst != 4);
+
+ for (i = 0; i < 4; ++i) {
+ u32 insn = le32_to_cpu(origptr[i]);
+
+ insn = aarch64_insn_encode_immediate(AARCH64_INSN_IMM_16,
+ insn,
+ addr & 0xffff);
+ BUG_ON(insn == AARCH64_BREAK_FAULT);
+ updptr[i] = cpu_to_le32(insn);
+ addr >>= 16;
+ }
+}
+
+static int create_hyp_debug_uart_mapping(void)
+{
+ if (is_kernel_in_hyp_mode())
+ return -EBUSY;
+
+ return __create_hyp_private_mapping(CONFIG_KVM_ARM_HYP_DEBUG_UART_ADDR,
+ PAGE_SIZE,
+ &__kvm_nvhe_arm64_kvm_hyp_debug_uart_addr,
+ PAGE_HYP_DEVICE);
+}
+#else
+static int create_hyp_debug_uart_mapping(void) { return 0; }
+#endif
+
/**
* create_hyp_io_mappings - Map IO into both kernel and HYP
* @phys_addr: The physical start address which gets mapped
@@ -1762,6 +1800,7 @@
goto out_destroy_pgtable;
io_map_base = hyp_idmap_start;
+ WARN_ON(create_hyp_debug_uart_mapping());
return 0;
out_destroy_pgtable:
