linux-kernel - [PATCH v2] x86/hyperv: use helpers to read control registers in hv_snp_boot

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Message-ID: <20240805201247.427982-1-yosryahmed@google.com>
Date: Mon,  5 Aug 2024 20:12:47 +0000
From: Yosry Ahmed <yosryahmed@...gle.com>
To: "K. Y. Srinivasan" <kys@...rosoft.com>, Haiyang Zhang <haiyangz@...rosoft.com>, 
	Wei Liu <wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>
Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, 
	"H. Peter Anvin" <hpa@...or.com>, linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Yosry Ahmed <yosryahmed@...gle.com>
Subject: [PATCH v2] x86/hyperv: use helpers to read control registers in hv_snp_boot_ap()

Use native_read_cr*() helpers to read control registers into vmsa->cr*
instead of open-coded assembly.

No functional change intended, unless there was a purpose to specifying
rax.

Signed-off-by: Yosry Ahmed <yosryahmed@...gle.com>
---

v1 -> v2:
- Fixed a silly bug that overwrote vmsa->cr3 instead of reading
  vmsa->cr0.

---
 arch/x86/hyperv/ivm.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/hyperv/ivm.c b/arch/x86/hyperv/ivm.c
index b4a851d27c7cb..60fc3ed728304 100644
--- a/arch/x86/hyperv/ivm.c
+++ b/arch/x86/hyperv/ivm.c
@@ -321,9 +321,9 @@ int hv_snp_boot_ap(u32 cpu, unsigned long start_ip)
 
 	vmsa->efer = native_read_msr(MSR_EFER);
 
-	asm volatile("movq %%cr4, %%rax;" : "=a" (vmsa->cr4));
-	asm volatile("movq %%cr3, %%rax;" : "=a" (vmsa->cr3));
-	asm volatile("movq %%cr0, %%rax;" : "=a" (vmsa->cr0));
+	vmsa->cr4 = native_read_cr4();
+	vmsa->cr3 = __native_read_cr3();
+	vmsa->cr0 = native_read_cr0();
 
 	vmsa->xcr0 = 1;
 	vmsa->g_pat = HV_AP_INIT_GPAT_DEFAULT;
-- 
2.46.0.rc2.264.g509ed76dc8-goog