[PATCH 3/5] KVM: e500: track host-writability of pages

Paolo Bonzini
2025-01-12T09:55:44Z

Add the possibility of marking a page so that the UW and SW bits are
force-cleared. This is stored in the private info so that it persists
across multiple calls to kvmppc_e500_setup_stlbe.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/powerpc/kvm/e500.h | 2 ++
arch/powerpc/kvm/e500_mmu_host.c | 15 +++++++++++----
2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/kvm/e500.h b/arch/powerpc/kvm/e500.h
index 6d0d329cbb35..f9acf866c709 100644
--- a/arch/powerpc/kvm/e500.h
+++ b/arch/powerpc/kvm/e500.h
@@ -34,6 +34,8 @@ enum vcpu_ftr {
#define E500_TLB_BITMAP (1 << 30)
/* TLB1 entry is mapped by host TLB0 */
#define E500_TLB_TLB0 (1 << 29)
+/* entry is writable on the host */
+#define E500_TLB_WRITABLE (1 << 28)
/* bits [6-5] MAS2_X1 and MAS2_X0 and [4-0] bits for WIMGE */
#define E500_TLB_MAS2_ATTR (0x7f)

diff --git a/arch/powerpc/kvm/e500_mmu_host.c b/arch/powerpc/kvm/e500_mmu_host.c
index c266c02f120f..b1be39639d4a 100644
--- a/arch/powerpc/kvm/e500_mmu_host.c
+++ b/arch/powerpc/kvm/e500_mmu_host.c
@@ -45,11 +45,14 @@ static inline unsigned int tlb1_max_shadow_size(void)
return host_tlb_params[1].entries - tlbcam_index - 1;
}

-static inline u32 e500_shadow_mas3_attrib(u32 mas3, int usermode)
+static inline u32 e500_shadow_mas3_attrib(u32 mas3, bool writable, int usermode)
{
/* Mask off reserved bits. */
mas3 &= MAS3_ATTRIB_MASK;

+ if (!writable)
+ mas3 &= ~(MAS3_UW|MAS3_SW);
+
#ifndef CONFIG_KVM_BOOKE_HV
if (!usermode) {
/* Guest is in supervisor mode,
@@ -244,10 +247,13 @@ static inline int tlbe_is_writable(struct kvm_book3e_206_tlb_entry *tlbe)

static inline void kvmppc_e500_ref_setup(struct tlbe_ref *ref,
struct kvm_book3e_206_tlb_entry *gtlbe,
- kvm_pfn_t pfn, unsigned int wimg)
+ kvm_pfn_t pfn, unsigned int wimg,
+ bool writable)
{
ref->pfn = pfn;
ref->flags = E500_TLB_VALID;
+ if (writable)
+ ref->flags |= E500_TLB_WRITABLE;

/* Use guest supplied MAS2_G and MAS2_E */
ref->flags |= (gtlbe->mas2 & MAS2_ATTRIB_MASK) | wimg;
@@ -303,6 +309,7 @@ static void kvmppc_e500_setup_stlbe(
{
kvm_pfn_t pfn = ref->pfn;
u32 pr = vcpu->arch.shared->msr & MSR_PR;
+ bool writable = !!(ref->flags & E500_TLB_WRITABLE);

BUG_ON(!(ref->flags & E500_TLB_VALID));

@@ -310,7 +317,7 @@ static void kvmppc_e500_setup_stlbe(
stlbe->mas1 = MAS1_TSIZE(tsize) | get_tlb_sts(gtlbe) | MAS1_VALID;
stlbe->mas2 = (gvaddr & MAS2_EPN) | (ref->flags & E500_TLB_MAS2_ATTR);
stlbe->mas7_3 = ((u64)pfn << PAGE_SHIFT) |
- e500_shadow_mas3_attrib(gtlbe->mas7_3, pr);
+ e500_shadow_mas3_attrib(gtlbe->mas7_3, writable, pr);
}

static inline int kvmppc_e500_shadow_map(struct kvmppc_vcpu_e500 *vcpu_e500,
@@ -487,7 +494,7 @@ static inline int kvmppc_e500_shadow_map(struct kvmppc_vcpu_e500 *vcpu_e500,
}
local_irq_restore(flags);

- kvmppc_e500_ref_setup(ref, gtlbe, pfn, wimg);
+ kvmppc_e500_ref_setup(ref, gtlbe, pfn, wimg, true);
kvmppc_e500_setup_stlbe(&vcpu_e500->vcpu, gtlbe, tsize,
ref, gvaddr, stlbe);
writable = tlbe_is_writable(stlbe);
--
2.47.1