[PATCH v5 1/6] KVM: SVM: Get rid of set_ghcb_msr() and *ghcb_msr_bits() functions

Joerg Roedel
2021-10-20T12:44:44Z

From: Joerg Roedel <jroedel@suse.de>

Replace the get_ghcb_msr_bits() function with macros and open code the
GHCB MSR setters with hypercall specific helper macros and functions.
This will avoid preserving any previous bits in the GHCB-MSR and
improves code readability.

Also get rid of the set_ghcb_msr() function and open-code it at its
call-sites for better code readability.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Reviewed-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/include/asm/sev-common.h | 9 +++++
arch/x86/kvm/svm/sev.c | 56 +++++++++++--------------------
2 files changed, 29 insertions(+), 36 deletions(-)

diff --git a/arch/x86/include/asm/sev-common.h b/arch/x86/include/asm/sev-common.h
index 2cef6c5a52c2..8540972cad04 100644
--- a/arch/x86/include/asm/sev-common.h
+++ b/arch/x86/include/asm/sev-common.h
@@ -50,6 +50,10 @@
(GHCB_MSR_CPUID_REQ | \
(((unsigned long)reg & GHCB_MSR_CPUID_REG_MASK) << GHCB_MSR_CPUID_REG_POS) | \
(((unsigned long)fn) << GHCB_MSR_CPUID_FUNC_POS))
+#define GHCB_MSR_CPUID_FN(msr) \
+ (((msr) >> GHCB_MSR_CPUID_FUNC_POS) & GHCB_MSR_CPUID_FUNC_MASK)
+#define GHCB_MSR_CPUID_REG(msr) \
+ (((msr) >> GHCB_MSR_CPUID_REG_POS) & GHCB_MSR_CPUID_REG_MASK)

/* AP Reset Hold */
#define GHCB_MSR_AP_RESET_HOLD_REQ 0x006
@@ -67,6 +71,11 @@
#define GHCB_SEV_TERM_REASON(reason_set, reason_val) \
(((((u64)reason_set) & GHCB_MSR_TERM_REASON_SET_MASK) << GHCB_MSR_TERM_REASON_SET_POS) | \
((((u64)reason_val) & GHCB_MSR_TERM_REASON_MASK) << GHCB_MSR_TERM_REASON_POS))
+#define GHCB_MSR_TERM_REASON_SET(msr) \
+ (((msr) >> GHCB_MSR_TERM_REASON_SET_POS) & GHCB_MSR_TERM_REASON_SET_MASK)
+#define GHCB_MSR_TERM_REASON(msr) \
+ (((msr) >> GHCB_MSR_TERM_REASON_POS) & GHCB_MSR_TERM_REASON_MASK)
+

#define GHCB_SEV_ES_REASON_GENERAL_REQUEST 0
#define GHCB_SEV_ES_REASON_PROTOCOL_UNSUPPORTED 1
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 3e2769855e51..2e3ecab6f1c8 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -2378,21 +2378,15 @@ static bool setup_vmgexit_scratch(struct vcpu_svm *svm, bool sync, u64 len)
return true;
}

-static void set_ghcb_msr_bits(struct vcpu_svm *svm, u64 value, u64 mask,
- unsigned int pos)
+static u64 ghcb_msr_cpuid_resp(u64 reg, u64 value)
{
- svm->vmcb->control.ghcb_gpa &= ~(mask << pos);
- svm->vmcb->control.ghcb_gpa |= (value & mask) << pos;
-}
+ u64 msr;

-static u64 get_ghcb_msr_bits(struct vcpu_svm *svm, u64 mask, unsigned int pos)
-{
- return (svm->vmcb->control.ghcb_gpa >> pos) & mask;
-}
+ msr = GHCB_MSR_CPUID_RESP;
+ msr |= (reg & GHCB_MSR_CPUID_REG_MASK) << GHCB_MSR_CPUID_REG_POS;
+ msr |= (value & GHCB_MSR_CPUID_VALUE_MASK) << GHCB_MSR_CPUID_VALUE_POS;

-static void set_ghcb_msr(struct vcpu_svm *svm, u64 value)
-{
- svm->vmcb->control.ghcb_gpa = value;
+ return msr;
}

static int sev_handle_vmgexit_msr_protocol(struct vcpu_svm *svm)
@@ -2409,16 +2403,14 @@ static int sev_handle_vmgexit_msr_protocol(struct vcpu_svm *svm)

switch (ghcb_info) {
case GHCB_MSR_SEV_INFO_REQ:
- set_ghcb_msr(svm, GHCB_MSR_SEV_INFO(GHCB_VERSION_MAX,
- GHCB_VERSION_MIN,
- sev_enc_bit));
+ svm->vmcb->control.ghcb_gpa = GHCB_MSR_SEV_INFO(GHCB_VERSION_MAX,
+ GHCB_VERSION_MIN,
+ sev_enc_bit);
break;
case GHCB_MSR_CPUID_REQ: {
u64 cpuid_fn, cpuid_reg, cpuid_value;

- cpuid_fn = get_ghcb_msr_bits(svm,
- GHCB_MSR_CPUID_FUNC_MASK,
- GHCB_MSR_CPUID_FUNC_POS);
+ cpuid_fn = GHCB_MSR_CPUID_FN(control->ghcb_gpa);

/* Initialize the registers needed by the CPUID intercept */
vcpu->arch.regs[VCPU_REGS_RAX] = cpuid_fn;
@@ -2430,9 +2422,8 @@ static int sev_handle_vmgexit_msr_protocol(struct vcpu_svm *svm)
break;
}

- cpuid_reg = get_ghcb_msr_bits(svm,
- GHCB_MSR_CPUID_REG_MASK,
- GHCB_MSR_CPUID_REG_POS);
+ cpuid_reg = GHCB_MSR_CPUID_REG(control->ghcb_gpa);
+
if (cpuid_reg == 0)
cpuid_value = vcpu->arch.regs[VCPU_REGS_RAX];
else if (cpuid_reg == 1)
@@ -2442,26 +2433,19 @@ static int sev_handle_vmgexit_msr_protocol(struct vcpu_svm *svm)
else
cpuid_value = vcpu->arch.regs[VCPU_REGS_RDX];

- set_ghcb_msr_bits(svm, cpuid_value,
- GHCB_MSR_CPUID_VALUE_MASK,
- GHCB_MSR_CPUID_VALUE_POS);
+ svm->vmcb->control.ghcb_gpa = ghcb_msr_cpuid_resp(cpuid_reg, cpuid_value);

- set_ghcb_msr_bits(svm, GHCB_MSR_CPUID_RESP,
- GHCB_MSR_INFO_MASK,
- GHCB_MSR_INFO_POS);
break;
}
case GHCB_MSR_TERM_REQ: {
u64 reason_set, reason_code;

- reason_set = get_ghcb_msr_bits(svm,
- GHCB_MSR_TERM_REASON_SET_MASK,
- GHCB_MSR_TERM_REASON_SET_POS);
- reason_code = get_ghcb_msr_bits(svm,
- GHCB_MSR_TERM_REASON_MASK,
- GHCB_MSR_TERM_REASON_POS);
+ reason_set = GHCB_MSR_TERM_REASON_SET(control->ghcb_gpa);
+ reason_code = GHCB_MSR_TERM_REASON(control->ghcb_gpa);
+
pr_info("SEV-ES guest requested termination: %#llx:%#llx\n",
reason_set, reason_code);
+
fallthrough;
}
default:
@@ -2637,9 +2621,9 @@ void sev_es_vcpu_reset(struct vcpu_svm *svm)
* Set the GHCB MSR value as per the GHCB specification when emulating
* vCPU RESET for an SEV-ES guest.
*/
- set_ghcb_msr(svm, GHCB_MSR_SEV_INFO(GHCB_VERSION_MAX,
- GHCB_VERSION_MIN,
- sev_enc_bit));
+ svm->vmcb->control.ghcb_gpa = GHCB_MSR_SEV_INFO(GHCB_VERSION_MAX,
+ GHCB_VERSION_MIN,
+ sev_enc_bit);
}

void sev_es_prepare_guest_switch(struct vcpu_svm *svm, unsigned int cpu)
--
2.33.1