[PATCH 5.10 289/290] KVM: arm64: Fix nVHE hyp panic host context restore

[gregkh]

From: Greg Kroah-Hartman <gre...@linuxfoundation.org>

From: Andrew Scull <asc...@google.com>

Commit c4b000c3928d4f20acef79dccf3a65ae3795e0b0 upstream.

When panicking from the nVHE hyp and restoring the host context, x29 is
expected to hold a pointer to the host context. This wasn't being done
so fix it to make sure there's a valid pointer the host context being
used.

Rather than passing a boolean indicating whether or not the host context
should be restored, instead pass the pointer to the host context. NULL
is passed to indicate that no context should be restored.

Fixes: a2e102e20fd6 ("KVM: arm64: nVHE: Handle hyp panics")
Cc: sta...@vger.kernel.org # 5.10.y only
Signed-off-by: Andrew Scull <asc...@google.com>
Signed-off-by: Marc Zyngier <m...@kernel.org>
Link: https://lore.kernel.org/r/20210219122406.1337626-1-asc...@google.com
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 arch/arm64/include/asm/kvm_hyp.h |    3 ++-
 arch/arm64/kvm/hyp/nvhe/host.S   |   20 ++++++++++----------
 arch/arm64/kvm/hyp/nvhe/switch.c |    3 +--
 3 files changed, 13 insertions(+), 13 deletions(-)

--- a/arch/arm64/include/asm/kvm_hyp.h
+++ b/arch/arm64/include/asm/kvm_hyp.h
@@ -99,7 +99,8 @@ u64 __guest_enter(struct kvm_vcpu *vcpu)
 
 void __noreturn hyp_panic(void);
 #ifdef __KVM_NVHE_HYPERVISOR__
-void __noreturn __hyp_do_panic(bool restore_host, u64 spsr, u64 elr, u64 par);
+void __noreturn __hyp_do_panic(struct kvm_cpu_context *host_ctxt, u64 spsr,
+                              u64 elr, u64 par);
 #endif
 
 #endif /* __ARM64_KVM_HYP_H__ */
--- a/arch/arm64/kvm/hyp/nvhe/host.S
+++ b/arch/arm64/kvm/hyp/nvhe/host.S
@@ -64,10 +64,15 @@ __host_enter_without_restoring:
 SYM_FUNC_END(__host_exit)
 
 /*
- * void __noreturn __hyp_do_panic(bool restore_host, u64 spsr, u64 elr, u64 
par);
+ * void __noreturn __hyp_do_panic(struct kvm_cpu_context *host_ctxt, u64 spsr,
+ *                               u64 elr, u64 par);
  */
 SYM_FUNC_START(__hyp_do_panic)
-       /* Load the format arguments into x1-7 */
+       mov     x29, x0
+
+       /* Load the format string into x0 and arguments into x1-7 */
+       ldr     x0, =__hyp_panic_string
+
        mov     x6, x3
        get_vcpu_ptr x7, x3
 
@@ -82,13 +87,8 @@ SYM_FUNC_START(__hyp_do_panic)
        ldr     lr, =panic
        msr     elr_el2, lr
 
-       /*
-        * Set the panic format string and enter the host, conditionally
-        * restoring the host context.
-        */
-       cmp     x0, xzr
-       ldr     x0, =__hyp_panic_string
-       b.eq    __host_enter_without_restoring
+       /* Enter the host, conditionally restoring the host context. */
+       cbz     x29, __host_enter_without_restoring
        b       __host_enter_for_panic
 SYM_FUNC_END(__hyp_do_panic)
 
@@ -144,7 +144,7 @@ SYM_FUNC_END(__hyp_do_panic)
 
 .macro invalid_host_el1_vect
        .align 7
-       mov     x0, xzr         /* restore_host = false */
+       mov     x0, xzr         /* host_ctxt = NULL */
        mrs     x1, spsr_el2
        mrs     x2, elr_el2
        mrs     x3, par_el1
--- a/arch/arm64/kvm/hyp/nvhe/switch.c
+++ b/arch/arm64/kvm/hyp/nvhe/switch.c
@@ -260,7 +260,6 @@ void __noreturn hyp_panic(void)
        u64 spsr = read_sysreg_el2(SYS_SPSR);
        u64 elr = read_sysreg_el2(SYS_ELR);
        u64 par = read_sysreg_par();
-       bool restore_host = true;
        struct kvm_cpu_context *host_ctxt;
        struct kvm_vcpu *vcpu;
 
@@ -274,7 +273,7 @@ void __noreturn hyp_panic(void)
                __sysreg_restore_state_nvhe(host_ctxt);
        }
 
-       __hyp_do_panic(restore_host, spsr, elr, par);
+       __hyp_do_panic(host_ctxt, spsr, elr, par);
        unreachable();
 }