[PATCH v5 08/13] KVM: arm64: Set an impdef ESR for Virtual-SError using VSESR_EL2.

James Morse
2017-12-15T15:50:09Z

Prior to v8.2's RAS Extensions, the HCR_EL2.VSE 'virtual SError' feature
generated an SError with an implementation defined ESR_EL1.ISS, because we
had no mechanism to specify the ESR value.

On Juno this generates an all-zero ESR, the most significant bit 'ISV'
is clear indicating the remainder of the ISS field is invalid.

With the RAS Extensions we have a mechanism to specify this value, and the
most significant bit has a new meaning: 'IDS - Implementation Defined
Syndrome'. An all-zero SError ESR now means: 'RAS error: Uncategorized'
instead of 'no valid ISS'.

Add KVM support for the VSESR_EL2 register to specify an ESR value when
HCR_EL2.VSE generates a virtual SError. Change kvm_inject_vabt() to
specify an implementation-defined value.

We only need to restore the VSESR_EL2 value when HCR_EL2.VSE is set, KVM
save/restores this bit during __{,de}activate_traps() and hardware clears the
bit once the guest has consumed the virtual-SError.

Future patches may add an API (or KVM CAP) to pend a virtual SError with
a specified ESR.

Cc: Dongjiu Geng <gengdongjiu@huawei.com>
Signed-off-by: James Morse <james.morse@arm.com>
Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
---
Changes since v4:
* Fixed an uncatagorized typo

arch/arm64/include/asm/kvm_emulate.h | 5 +++++
arch/arm64/include/asm/kvm_host.h | 3 +++
arch/arm64/include/asm/sysreg.h | 1 +
arch/arm64/kvm/hyp/switch.c | 3 +++
arch/arm64/kvm/inject_fault.c | 13 ++++++++++++-
5 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
index 5f28dfa14cee..6d3614795197 100644
--- a/arch/arm64/include/asm/kvm_emulate.h
+++ b/arch/arm64/include/asm/kvm_emulate.h
@@ -64,6 +64,11 @@ static inline void vcpu_set_hcr(struct kvm_vcpu *vcpu, unsigned long hcr)
vcpu->arch.hcr_el2 = hcr;
}

+static inline void vcpu_set_vsesr(struct kvm_vcpu *vcpu, u64 vsesr)
+{
+ vcpu->arch.vsesr_el2 = vsesr;
+}
+
static inline unsigned long *vcpu_pc(const struct kvm_vcpu *vcpu)
{
return (unsigned long *)&vcpu_gp_regs(vcpu)->regs.pc;
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 4a4764630d98..c626c081ce9a 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -278,6 +278,9 @@ struct kvm_vcpu_arch {

/* Detect first run of a vcpu */
bool has_run_once;
+
+ /* Virtual SError ESR to restore when HCR_EL2.VSE is set */
+ u64 vsesr_el2;
};

#define vcpu_gp_regs(v) (&(v)->arch.ctxt.gp_regs)
diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index 3f859000439f..6afbf2334763 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -355,6 +355,7 @@

#define SYS_DACR32_EL2 sys_reg(3, 4, 3, 0, 0)
#define SYS_IFSR32_EL2 sys_reg(3, 4, 5, 0, 1)
+#define SYS_VSESR_EL2 sys_reg(3, 4, 5, 2, 3)
#define SYS_FPEXC32_EL2 sys_reg(3, 4, 5, 3, 0)

#define __SYS__AP0Rx_EL2(x) sys_reg(3, 4, 12, 8, x)
diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
index f7c651f3a8c0..51e65fc1b0cd 100644
--- a/arch/arm64/kvm/hyp/switch.c
+++ b/arch/arm64/kvm/hyp/switch.c
@@ -93,6 +93,9 @@ static void __hyp_text __activate_traps(struct kvm_vcpu *vcpu)

write_sysreg(val, hcr_el2);

+ if (cpus_have_const_cap(ARM64_HAS_RAS_EXTN) && (val & HCR_VSE))
+ write_sysreg_s(vcpu->arch.vsesr_el2, SYS_VSESR_EL2);
+
/* Trap on AArch32 cp15 c15 accesses (EL1 or EL0) */
write_sysreg(1 << 15, hstr_el2);
/*
diff --git a/arch/arm64/kvm/inject_fault.c b/arch/arm64/kvm/inject_fault.c
index 8ecbcb40e317..60666a056944 100644
--- a/arch/arm64/kvm/inject_fault.c
+++ b/arch/arm64/kvm/inject_fault.c
@@ -164,14 +164,25 @@ void kvm_inject_undefined(struct kvm_vcpu *vcpu)
inject_undef64(vcpu);
}

+static void pend_guest_serror(struct kvm_vcpu *vcpu, u64 esr)
+{
+ vcpu_set_vsesr(vcpu, esr);
+ vcpu_set_hcr(vcpu, vcpu_get_hcr(vcpu) | HCR_VSE);
+}
+
/**
* kvm_inject_vabt - inject an async abort / SError into the guest
* @vcpu: The VCPU to receive the exception
*
* It is assumed that this code is called from the VCPU thread and that the
* VCPU therefore is not currently executing guest code.
+ *
+ * Systems with the RAS Extensions specify an imp-def ESR (ISV/IDS = 1) with
+ * the remaining ISS all-zeros so that this error is not interpreted as an
+ * uncategorized RAS error. Without the RAS Extensions we can't specify an ESR
+ * value, so the CPU generates an imp-def value.
*/
void kvm_inject_vabt(struct kvm_vcpu *vcpu)
{
- vcpu_set_hcr(vcpu, vcpu_get_hcr(vcpu) | HCR_VSE);
+ pend_guest_serror(vcpu, ESR_ELx_ISV);
}
--
2.15.0