Re: [PATCH] KVM: x86/mmu: improve robustness of some functions

Vitaly Kuznetsov
2021-01-26T05:23:33Z

Stephen Zhang <stephenzhangzsd@gmail.com> writes:

> If the name of this function changes, you can easily
> forget to modify the code in the corresponding place.
> In fact, such errors already exist in spte_write_protect
> and spte_clear_dirty.
>

What if we do something like (completely untested):

diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h
index bfc6389edc28..5ec15e4160b1 100644
--- a/arch/x86/kvm/mmu/mmu_internal.h
+++ b/arch/x86/kvm/mmu/mmu_internal.h
@@ -12,7 +12,7 @@
extern bool dbg;

#define pgprintk(x...) do { if (dbg) printk(x); } while (0)
-#define rmap_printk(x...) do { if (dbg) printk(x); } while (0)
+#define rmap_printk(fmt, args...) do { if (dbg) printk("%s: " fmt, __func__, ## args); } while (0)
#define MMU_WARN_ON(x) WARN_ON(x)
#else
#define pgprintk(x...) do { } while (0)

and eliminate the need to pass '__func__,' explicitly? We can probably
do the same to pgprintk().

> Signed-off-by: Stephen Zhang <stephenzhangzsd@gmail.com>
> ---
> arch/x86/kvm/mmu/mmu.c | 16 ++++++++--------
> 1 file changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 6d16481..09462c3d 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -844,17 +844,17 @@ static int pte_list_add(struct kvm_vcpu *vcpu, u64 *spte,
> int i, count = 0;
>
> if (!rmap_head->val) {
> - rmap_printk("pte_list_add: %p %llx 0->1\n", spte, *spte);
> + rmap_printk("%s: %p %llx 0->1\n", __func__, spte, *spte);
> rmap_head->val = (unsigned long)spte;
> } else if (!(rmap_head->val & 1)) {
> - rmap_printk("pte_list_add: %p %llx 1->many\n", spte, *spte);
> + rmap_printk("%s: %p %llx 1->many\n", __func__, spte, *spte);
> desc = mmu_alloc_pte_list_desc(vcpu);
> desc->sptes[0] = (u64 *)rmap_head->val;
> desc->sptes[1] = spte;
> rmap_head->val = (unsigned long)desc | 1;
> ++count;
> } else {
> - rmap_printk("pte_list_add: %p %llx many->many\n", spte, *spte);
> + rmap_printk("%s: %p %llx many->many\n", __func__, spte, *spte);
> desc = (struct pte_list_desc *)(rmap_head->val & ~1ul);
> while (desc->sptes[PTE_LIST_EXT-1]) {
> count += PTE_LIST_EXT;
> @@ -1115,7 +1115,7 @@ static bool spte_write_protect(u64 *sptep, bool pt_protect)
> !(pt_protect && spte_can_locklessly_be_made_writable(spte)))
> return false;
>
> - rmap_printk("rmap_write_protect: spte %p %llx\n", sptep, *sptep);
> + rmap_printk("%s: spte %p %llx\n", __func__, sptep, *sptep);
>
> if (pt_protect)
> spte &= ~SPTE_MMU_WRITEABLE;
> @@ -1142,7 +1142,7 @@ static bool spte_clear_dirty(u64 *sptep)
> {
> u64 spte = *sptep;
>
> - rmap_printk("rmap_clear_dirty: spte %p %llx\n", sptep, *sptep);
> + rmap_printk("%s: spte %p %llx\n", __func__, sptep, *sptep);
>
> MMU_WARN_ON(!spte_ad_enabled(spte));
> spte &= ~shadow_dirty_mask;
> @@ -1184,7 +1184,7 @@ static bool spte_set_dirty(u64 *sptep)
> {
> u64 spte = *sptep;
>
> - rmap_printk("rmap_set_dirty: spte %p %llx\n", sptep, *sptep);
> + rmap_printk("%s: spte %p %llx\n", __func__, sptep, *sptep);
>
> /*
> * Similar to the !kvm_x86_ops.slot_disable_log_dirty case,
> @@ -1363,8 +1363,8 @@ static int kvm_set_pte_rmapp(struct kvm *kvm, struct kvm_rmap_head *rmap_head,
>
> restart:
> for_each_rmap_spte(rmap_head, &iter, sptep) {
> - rmap_printk("kvm_set_pte_rmapp: spte %p %llx gfn %llx (%d)\n",
> - sptep, *sptep, gfn, level);
> + rmap_printk("%s: spte %p %llx gfn %llx (%d)\n",
> + __func__, sptep, *sptep, gfn, level);
>
> need_flush = 1;

--
Vitaly