[PATCH v11 06/45] x86/boot: Use MSR read/write helpers instead of inline assembly

Brijesh Singh
2022-02-24T16:58:46Z

From: Michael Roth <michael.roth@amd.com>

Update all C code to use the new boot_rdmsr()/boot_wrmsr() helpers
instead of relying on inline assembly.

Suggested-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Michael Roth <michael.roth@amd.com>
---
arch/x86/boot/compressed/sev.c | 17 +++++++----------
arch/x86/boot/cpucheck.c | 30 +++++++++++++++---------------
2 files changed, 22 insertions(+), 25 deletions(-)

diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c
index 28bcf04c022e..4e82101b7d13 100644
--- a/arch/x86/boot/compressed/sev.c
+++ b/arch/x86/boot/compressed/sev.c
@@ -22,6 +22,7 @@
#include <asm/svm.h>

#include "error.h"
+#include "../msr.h"

struct ghcb boot_ghcb_page __aligned(PAGE_SIZE);
struct ghcb *boot_ghcb;
@@ -56,23 +57,19 @@ static unsigned long insn_get_seg_base(struct pt_regs *regs, int seg_reg_idx)

static inline u64 sev_es_rd_ghcb_msr(void)
{
- unsigned long low, high;
+ struct msr m;

- asm volatile("rdmsr" : "=a" (low), "=d" (high) :
- "c" (MSR_AMD64_SEV_ES_GHCB));
+ boot_rdmsr(MSR_AMD64_SEV_ES_GHCB, &m);

- return ((high << 32) | low);
+ return m.q;
}

static inline void sev_es_wr_ghcb_msr(u64 val)
{
- u32 low, high;
+ struct msr m;

- low = val & 0xffffffffUL;
- high = val >> 32;
-
- asm volatile("wrmsr" : : "c" (MSR_AMD64_SEV_ES_GHCB),
- "a"(low), "d" (high) : "memory");
+ m.q = val;
+ boot_wrmsr(MSR_AMD64_SEV_ES_GHCB, &m);
}

static enum es_result vc_decode_insn(struct es_em_ctxt *ctxt)
diff --git a/arch/x86/boot/cpucheck.c b/arch/x86/boot/cpucheck.c
index e1478d32de1a..fed8d13ce252 100644
--- a/arch/x86/boot/cpucheck.c
+++ b/arch/x86/boot/cpucheck.c
@@ -27,6 +27,7 @@
#include <asm/required-features.h>
#include <asm/msr-index.h>
#include "string.h"
+#include "msr.h"

static u32 err_flags[NCAPINTS];

@@ -130,12 +131,11 @@ int check_cpu(int *cpu_level_ptr, int *req_level_ptr, u32 **err_flags_ptr)
/* If this is an AMD and we're only missing SSE+SSE2, try to
turn them on */

- u32 ecx = MSR_K7_HWCR;
- u32 eax, edx;
+ struct msr m;

- asm("rdmsr" : "=a" (eax), "=d" (edx) : "c" (ecx));
- eax &= ~(1 << 15);
- asm("wrmsr" : : "a" (eax), "d" (edx), "c" (ecx));
+ boot_rdmsr(MSR_K7_HWCR, &m);
+ m.l &= ~(1 << 15);
+ boot_wrmsr(MSR_K7_HWCR, &m);

get_cpuflags(); /* Make sure it really did something */
err = check_cpuflags();
@@ -145,28 +145,28 @@ int check_cpu(int *cpu_level_ptr, int *req_level_ptr, u32 **err_flags_ptr)
/* If this is a VIA C3, we might have to enable CX8
explicitly */

- u32 ecx = MSR_VIA_FCR;
- u32 eax, edx;
+ struct msr m;

- asm("rdmsr" : "=a" (eax), "=d" (edx) : "c" (ecx));
- eax |= (1<<1)|(1<<7);
- asm("wrmsr" : : "a" (eax), "d" (edx), "c" (ecx));
+ boot_rdmsr(MSR_VIA_FCR, &m);
+ m.l |= (1 << 1) | (1 << 7);
+ boot_wrmsr(MSR_VIA_FCR, &m);

set_bit(X86_FEATURE_CX8, cpu.flags);
err = check_cpuflags();
} else if (err == 0x01 && is_transmeta()) {
/* Transmeta might have masked feature bits in word 0 */

- u32 ecx = 0x80860004;
- u32 eax, edx;
+ struct msr m, m_tmp;
u32 level = 1;

- asm("rdmsr" : "=a" (eax), "=d" (edx) : "c" (ecx));
- asm("wrmsr" : : "a" (~0), "d" (edx), "c" (ecx));
+ boot_rdmsr(0x80860004, &m);
+ m_tmp = m;
+ m_tmp.l = ~0;
+ boot_wrmsr(0x80860004, &m_tmp);
asm("cpuid"
: "+a" (level), "=d" (cpu.flags[0])
: : "ecx", "ebx");
- asm("wrmsr" : : "a" (eax), "d" (edx), "c" (ecx));
+ boot_wrmsr(0x80860004, &m);

err = check_cpuflags();
} else if (err == 0x01 &&
--
2.25.1