linux-kernel - [RFC 06/26] KVM: VMX: Add helpers to handle the writes to MSR's R/O and R/WC0 bits

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Date: Sat,  3 Feb 2024 17:11:54 +0800
From: Zhao Liu <zhao1.liu@...ux.intel.com>
To: Paolo Bonzini <pbonzini@...hat.com>,
	Sean Christopherson <seanjc@...gle.com>,
	"Rafael J . Wysocki" <rafael@...nel.org>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H . Peter Anvin" <hpa@...or.com>,
	kvm@...r.kernel.org,
	linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	x86@...nel.org
Cc: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>,
	Len Brown <len.brown@...el.com>,
	Zhang Rui <rui.zhang@...el.com>,
	Zhenyu Wang <zhenyu.z.wang@...el.com>,
	Zhuocheng Ding <zhuocheng.ding@...el.com>,
	Dapeng Mi <dapeng1.mi@...el.com>,
	Yanting Jiang <yanting.jiang@...el.com>,
	Yongwei Ma <yongwei.ma@...el.com>,
	Vineeth Pillai <vineeth@...byteword.org>,
	Suleiman Souhlal <suleiman@...gle.com>,
	Masami Hiramatsu <mhiramat@...gle.com>,
	David Dai <davidai@...gle.com>,
	Saravana Kannan <saravanak@...gle.com>,
	Zhao Liu <zhao1.liu@...el.com>
Subject: [RFC 06/26] KVM: VMX: Add helpers to handle the writes to MSR's R/O and R/WC0 bits

From: Zhao Liu <zhao1.liu@...el.com>

For WRMSR emulation, any write to R/O bit and any nonzero write to R/WC0
bit must be ignored.

Provide 2 helpers to emulate the above R/O and R/WC0 write behavior.

Tested-by: Yanting Jiang <yanting.jiang@...el.com>
Signed-off-by: Zhao Liu <zhao1.liu@...el.com>
---
 arch/x86/kvm/vmx/vmx.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index e262bc2ba4e5..8f5981635fe5 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -2147,6 +2147,20 @@ static u64 vmx_get_supported_debugctl(struct kvm_vcpu *vcpu, bool host_initiated
 	return debugctl;
 }
 
+/* Ignore writes to R/O bits. */
+static inline u64 vmx_set_msr_ro_bits(u64 new_val, u64 old_val, u64 ro_mask)
+{
+	return (new_val & ~ro_mask) | (old_val & ro_mask);
+}
+
+/* Ignore non-zero writes to R/WC0 bits. */
+static inline u64 vmx_set_msr_rwc0_bits(u64 new_val, u64 old_val, u64 rwc0_mask)
+{
+	u64 new_rwc0 = new_val & rwc0_mask, old_rwc0 = old_val & rwc0_mask;
+
+	return ((new_rwc0 | ~old_rwc0) & old_rwc0) | (new_val & ~rwc0_mask);
+}
+
 /*
  * Writes msr value into the appropriate "register".
  * Returns 0 on success, non-0 otherwise.
-- 
2.34.1