Messages in this thread | | | Date | Mon, 23 Oct 2023 14:45:41 +0000 | From | Sebastian Ene <> | Subject | Re: [PATCH v2 11/11] arm64: ptdump: Add support for guest stage-2 pagetables dumping |
| |
On Fri, Oct 20, 2023 at 09:40:06AM +0100, Vincent Donnefort wrote: > On Thu, Oct 19, 2023 at 02:40:33PM +0000, Sebastian Ene wrote: > > Register a debugfs file on guest creation to be able to view their > > second translation tables with ptdump. This assumes that the host is in > > control of the guest stage-2 and has direct access to the pagetables. > > What about pKVM? The walker you wrote for the host stage-2 should be > reusable in that case? >
Yes, when pKVM will be ready upstream the walker which duplicates the pagetables for the host will be re-used for the guests. We will have to add a separate HVC for this which receives as an argument the guest vmid.
> > > > Signed-off-by: Sebastian Ene <sebastianene@google.com> > > --- > > arch/arm64/include/asm/ptdump.h | 21 +++++++-- > > arch/arm64/kvm/mmu.c | 3 ++ > > arch/arm64/mm/ptdump.c | 84 +++++++++++++++++++++++++++++++++ > > arch/arm64/mm/ptdump_debugfs.c | 5 +- > > 4 files changed, 108 insertions(+), 5 deletions(-) > > > > diff --git a/arch/arm64/include/asm/ptdump.h b/arch/arm64/include/asm/ptdump.h > > index 35b883524462..be86244d532b 100644 > > --- a/arch/arm64/include/asm/ptdump.h > > +++ b/arch/arm64/include/asm/ptdump.h > > @@ -5,6 +5,8 @@ > > #ifndef __ASM_PTDUMP_H > > #define __ASM_PTDUMP_H > > > > +#include <asm/kvm_pgtable.h> > > + > > #ifdef CONFIG_PTDUMP_CORE > > > > #include <linux/mm_types.h> > > @@ -30,14 +32,27 @@ struct ptdump_info { > > void ptdump_walk(struct seq_file *s, struct ptdump_info *info); > > #ifdef CONFIG_PTDUMP_DEBUGFS > > #define EFI_RUNTIME_MAP_END DEFAULT_MAP_WINDOW_64 > > -void __init ptdump_debugfs_register(struct ptdump_info *info, const char *name); > > +struct dentry *ptdump_debugfs_register(struct ptdump_info *info, > > + const char *name); > > #else > > -static inline void ptdump_debugfs_register(struct ptdump_info *info, > > - const char *name) { } > > +static inline struct dentry *ptdump_debugfs_register(struct ptdump_info *info, > > + const char *name) > > +{ > > + return NULL; > > +} > > #endif > > void ptdump_check_wx(void); > > #endif /* CONFIG_PTDUMP_CORE */ > > > > +#ifdef CONFIG_NVHE_EL2_PTDUMP_DEBUGFS > > +void ptdump_register_guest_stage2(struct kvm_pgtable *pgt, void *lock); > > +void ptdump_unregister_guest_stage2(struct kvm_pgtable *pgt); > > +#else > > +static inline void ptdump_register_guest_stage2(struct kvm_pgtable *pgt, > > + void *lock) { } > > +static inline void ptdump_unregister_guest_stage2(struct kvm_pgtable *pgt) { } > > +#endif /* CONFIG_NVHE_EL2_PTDUMP_DEBUGFS */ > > I believe this should be compatible with VHE as well, that option should be > renamed. >
Good point, I will rename this.
> > + > > #ifdef CONFIG_DEBUG_WX > > #define debug_checkwx() ptdump_check_wx() > > #else > > diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c > > index 482280fe22d7..e47988dba34d 100644 > > --- a/arch/arm64/kvm/mmu.c > > +++ b/arch/arm64/kvm/mmu.c > > @@ -11,6 +11,7 @@ > > #include <linux/sched/signal.h> > > #include <trace/events/kvm.h> > > #include <asm/pgalloc.h> > > +#include <asm/ptdump.h> > > #include <asm/cacheflush.h> > > #include <asm/kvm_arm.h> > > #include <asm/kvm_mmu.h> > > @@ -908,6 +909,7 @@ int kvm_init_stage2_mmu(struct kvm *kvm, struct kvm_s2_mmu *mmu, unsigned long t > > if (err) > > goto out_free_pgtable; > > > > + ptdump_register_guest_stage2(pgt, &kvm->mmu_lock); > > mmu->last_vcpu_ran = alloc_percpu(typeof(*mmu->last_vcpu_ran)); > > if (!mmu->last_vcpu_ran) { > > err = -ENOMEM; > > @@ -1021,6 +1023,7 @@ void kvm_free_stage2_pgd(struct kvm_s2_mmu *mmu) > > write_unlock(&kvm->mmu_lock); > > > > if (pgt) { > > + ptdump_unregister_guest_stage2(pgt); > > kvm_pgtable_stage2_destroy(pgt); > > kfree(pgt); > > } > > diff --git a/arch/arm64/mm/ptdump.c b/arch/arm64/mm/ptdump.c > > index 4687840dcb69..facfb15468f5 100644 > > --- a/arch/arm64/mm/ptdump.c > > +++ b/arch/arm64/mm/ptdump.c > > @@ -26,6 +26,7 @@ > > #include <asm/ptdump.h> > > #include <asm/kvm_pkvm.h> > > #include <asm/kvm_pgtable.h> > > +#include <asm/kvm_host.h> > > > > > > enum address_markers_idx { > > @@ -543,6 +544,22 @@ void ptdump_check_wx(void) > > #ifdef CONFIG_NVHE_EL2_PTDUMP_DEBUGFS > > static struct ptdump_info stage2_kernel_ptdump_info; > > > > +#define GUEST_NAME_LEN (32U) > > + > > +struct ptdump_registered_guest { > > + struct list_head reg_list; > > + struct ptdump_info info; > > + struct mm_struct mem; > > + struct kvm_pgtable_snapshot snapshot; > > + struct dentry *dentry; > > + rwlock_t *lock; > > + char reg_name[GUEST_NAME_LEN]; > > +}; > > + > > +static LIST_HEAD(ptdump_guest_list); > > +static DEFINE_MUTEX(ptdump_list_lock); > > +static u16 guest_no; > > This is not robust enough: If 1 VM starts then 65535 others which are killed. > guest_no overflows. The next number is 0 which is already taken. >
Yes, I guess this should be improved. In the case you described we won't register any debugfs file because of the name clash.
> Linux has and ID allocation to solve this problem, but I don't think this is > necessary anyway. This should simply reuse the struct kvm->debugfs_dentry. > > Also probably most of the informations contained in ptdump_registered_guest can > be found in struct kvm. The debugfs should then probably simply take struct kvm > for the private argument. >
I would prefer to keep it as a separate struct here as it gives some flexibility if we need to extend it for guests pKVM support. I think we can drop the struct mm_struct from here.
Thanks, Sebastian
> > + > > static phys_addr_t ptdump_host_pa(void *addr) > > { > > return __pa(addr); > > @@ -740,6 +757,73 @@ static void stage2_ptdump_walk(struct seq_file *s, struct ptdump_info *info) > > > > kvm_pgtable_walk(pgtable, start_ipa, end_ipa, &walker); > > } > > [...]
| |