From mboxrd@z Thu Jan 1 00:00:00 1970 From: christoffer.dall@linaro.org (Christoffer Dall) Date: Tue, 7 Oct 2014 21:39:54 +0200 Subject: [PATCH v2 1/3] arm64: KVM: Implement 48 VA support for KVM EL2 and Stage-2 In-Reply-To: <5433EA8B.6010502@arm.com> References: <1412627427-28629-1-git-send-email-christoffer.dall@linaro.org> <1412627427-28629-2-git-send-email-christoffer.dall@linaro.org> <20141007104846.GB12675@e104818-lin.cambridge.arm.com> <5433EA8B.6010502@arm.com> Message-ID: <20141007193954.GI3717@cbox> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Tue, Oct 07, 2014 at 02:28:43PM +0100, Marc Zyngier wrote: > On 07/10/14 11:48, Catalin Marinas wrote: > > On Mon, Oct 06, 2014 at 09:30:25PM +0100, Christoffer Dall wrote: > >> +/** > >> + * kvm_prealloc_hwpgd - allocate inital table for VTTBR > >> + * @kvm: The KVM struct pointer for the VM. > >> + * @pgd: The kernel pseudo pgd > >> + * > >> + * When the kernel uses more levels of page tables than the guest, we allocate > >> + * a fake PGD and pre-populate it to point to the next-level page table, which > >> + * will be the real initial page table pointed to by the VTTBR. > >> + * > >> + * When KVM_PREALLOC_LEVEL==2, we allocate a single page for the PMD and > >> + * the kernel will use folded pud. When KVM_PREALLOC_LEVEL==1, we > >> + * allocate 2 consecutive PUD pages. > >> + */ > >> +#if defined(CONFIG_ARM64_64K_PAGES) && CONFIG_ARM64_PGTABLE_LEVELS == 3 > >> +#define KVM_PREALLOC_LEVEL 2 > >> +#define PTRS_PER_S2_PGD 1 > >> +#define S2_PGD_ORDER get_order(PTRS_PER_S2_PGD * sizeof(pgd_t)) > > > > I agree that my magic equation wasn't readable ;) (I had troubles > > re-understanding it as well), but you also have some constants here that > > are not immediately obvious where you got to them from. IIUC, > > KVM_PREALLOC_LEVEL == 2 here means that the hardware only understands > > stage 2 pmd and pte. I guess you could look into the ARM ARM tables but > > it's still not clear. > > > > Let's look at PTRS_PER_S2_PGD as I think it's simpler. My proposal was: > > > > #if PGDIR_SHIFT > KVM_PHYS_SHIFT > > #define PTRS_PER_S2_PGD (1) > > #else > > #define PTRS_PER_S2_PGD (1 << (KVM_PHYS_SHIFT - PGDIR_SHIFT)) > > #endif > > > > In this case PGDIR_SHIFT is 42, so we get PTRS_PER_S2_PGD == 1. The 4K > > and 4 levels case below is also correct. > > > > The KVM start level calculation, we could assume that KVM needs either > > host levels or host levels - 1 (unless we go for some weirdly small > > KVM_PHYS_SHIFT). So we could define them KVM_PREALLOC_LEVEL as: > > > > #if PTRS_PER_S2_PGD <= 16 > > #define KVM_PREALLOC_LEVEL (4 - CONFIG_ARM64_PGTABLE_LEVELS + 1) > > #else > > #define KVM_PREALLOC_LEVEL (0) > > #endif > > > > Basically if you can concatenate 16 or less pages at the level below the > > top, the architecture does not allow a small top level. In this case, > > (4 - CONFIG_ARM64_PGTABLE_LEVELS) represents the first level for the > > host and we add 1 to go to the next level for KVM stage 2 when > > PTRS_PER_S2_PGD is 16 or less. We use 0 when we don't need to > > preallocate. > > I think this makes the whole thing clearer (at least for me), as it > makes the relationship between KVM_PREALLOC_LEVEL and > CONFIG_ARM64_PGTABLE_LEVELS explicit (it wasn't completely obvious to me > initially). Agreed. > > >> +static inline int kvm_prealloc_hwpgd(struct kvm *kvm, pgd_t *pgd) > >> +{ > >> + pud_t *pud; > >> + pmd_t *pmd; > >> + > >> + pud = pud_offset(pgd, 0); > >> + pmd = (pmd_t *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, 0); > >> + > >> + if (!pmd) > >> + return -ENOMEM; > >> + pud_populate(NULL, pud, pmd); > >> + > >> + return 0; > >> +} > >> + > >> +static inline void kvm_free_hwpgd(struct kvm *kvm) > >> +{ > >> + pgd_t *pgd = kvm->arch.pgd; > >> + pud_t *pud = pud_offset(pgd, 0); > >> + pmd_t *pmd = pmd_offset(pud, 0); > >> + free_pages((unsigned long)pmd, 0); > >> +} > >> + > >> +static inline phys_addr_t kvm_get_hwpgd(struct kvm *kvm) > >> +{ > >> + pgd_t *pgd = kvm->arch.pgd; > >> + pud_t *pud = pud_offset(pgd, 0); > >> + pmd_t *pmd = pmd_offset(pud, 0); > >> + return virt_to_phys(pmd); > >> + > >> +} > >> +#elif defined(CONFIG_ARM64_4K_PAGES) && CONFIG_ARM64_PGTABLE_LEVELS == 4 > >> +#define KVM_PREALLOC_LEVEL 1 > >> +#define PTRS_PER_S2_PGD 2 > >> +#define S2_PGD_ORDER get_order(PTRS_PER_S2_PGD * sizeof(pgd_t)) > > > > Here PGDIR_SHIFT is 39, so we get PTRS_PER_S2_PGD == (1 << (40 - 39)) > > which is 2 and KVM_PREALLOC_LEVEL == 1. > > > >> +static inline int kvm_prealloc_hwpgd(struct kvm *kvm, pgd_t *pgd) > >> +{ > >> + pud_t *pud; > >> + > >> + pud = (pud_t *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, 1); > >> + if (!pud) > >> + return -ENOMEM; > >> + pgd_populate(NULL, pgd, pud); > >> + pgd_populate(NULL, pgd + 1, pud + PTRS_PER_PUD); > >> + > >> + return 0; > >> +} > > > > You still need to define these functions but you can make their > > implementation dependent solely on the KVM_PREALLOC_LEVEL rather than > > 64K/4K and levels combinations. If it is KVM_PREALLOC_LEVEL is 1, you > > allocate pud and populate the pgds (in a loop based on the > > PTRS_PER_S2_PGD). If it is 2, you allocate the pmd and populate the pud > > (still in a loop though it would probably be 1 iteration). We know based > > on the assumption above that you can't get KVM_PREALLOC_LEVEL == 2 and > > CONFIG_ARM64_PGTABLE_LEVELS == 4. > > > > Also agreed. Most of what you wrote here could also be gathered as > comments in the patch. > Yes, I reworded some of the text slightly as comments for the next version of the patch. However, I'm not sure I have a clear idea of how you'd like these functions to look like. I came up with the following based on your feedback, but I personally don't find it a lot easier to read than what I had already. Suggestions are welcome: diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h index a030d16..7941a51 100644 --- a/arch/arm64/include/asm/kvm_mmu.h +++ b/arch/arm64/include/asm/kvm_mmu.h @@ -41,6 +41,18 @@ */ #define TRAMPOLINE_VA (HYP_PAGE_OFFSET_MASK & PAGE_MASK) +/* + * KVM_MMU_CACHE_MIN_PAGES is the number of stage2 page table translation + * levels in addition to the PGD and potentially the PUD which are + * pre-allocated (we pre-allocate the fake PGD and the PUD when the Stage-2 + * tables use one level of tables less than the kernel. + */ +#ifdef CONFIG_ARM64_64K_PAGES +#define KVM_MMU_CACHE_MIN_PAGES 1 +#else +#define KVM_MMU_CACHE_MIN_PAGES 2 +#endif + #ifdef __ASSEMBLY__ /* @@ -53,6 +65,7 @@ #else +#include #include #include @@ -65,10 +78,6 @@ #define KVM_PHYS_SIZE (1UL << KVM_PHYS_SHIFT) #define KVM_PHYS_MASK (KVM_PHYS_SIZE - 1UL) -/* Make sure we get the right size, and thus the right alignment */ -#define PTRS_PER_S2_PGD (1 << (KVM_PHYS_SHIFT - PGDIR_SHIFT)) -#define S2_PGD_ORDER get_order(PTRS_PER_S2_PGD * sizeof(pgd_t)) - int create_hyp_mappings(void *from, void *to); int create_hyp_io_mappings(void *from, void *to, phys_addr_t); void free_boot_hyp_pgd(void); @@ -93,6 +102,7 @@ void kvm_clear_hyp_idmap(void); #define kvm_set_pmd(pmdp, pmd) set_pmd(pmdp, pmd) static inline void kvm_clean_pgd(pgd_t *pgd) {} +static inline void kvm_clean_pmd(pmd_t *pmd) {} static inline void kvm_clean_pmd_entry(pmd_t *pmd) {} static inline void kvm_clean_pte(pte_t *pte) {} static inline void kvm_clean_pte_entry(pte_t *pte) {} @@ -118,13 +128,115 @@ static inline bool kvm_page_empty(void *ptr) } #define kvm_pte_table_empty(ptep) kvm_page_empty(ptep) -#ifndef CONFIG_ARM64_64K_PAGES -#define kvm_pmd_table_empty(pmdp) kvm_page_empty(pmdp) -#else + +#ifdef __PAGETABLE_PMD_FOLDED #define kvm_pmd_table_empty(pmdp) (0) +#else +#define kvm_pmd_table_empty(pmdp) kvm_page_empty(pmdp) #endif + +#ifdef __PAGETABLE_PUD_FOLDED #define kvm_pud_table_empty(pudp) (0) +#else +#define kvm_pud_table_empty(pudp) kvm_page_empty(pudp) +#endif + +/* + * In the case where PGDIR_SHIFT is larger than KVM_PHYS_SHIFT, we can address + * the entire IPA input range with a single pgd entry, and we would only need + * one pgd entry. + */ +#if PGDIR_SHIFT > KVM_PHYS_SHIFT +#define PTRS_PER_S2_PGD (1) +#else +#define PTRS_PER_S2_PGD (1 << (KVM_PHYS_SHIFT - PGDIR_SHIFT)) +#endif +#define S2_PGD_ORDER get_order(PTRS_PER_S2_PGD * sizeof(pgd_t)) +/* + * If we are concatenating first level stage-2 page tables, we would have less + * than or equal to 16 pointers in the fake PGD, because that's what the + * architecture allows. In this case, (4 - CONFIG_ARM64_PGTABLE_LEVELS) + * represents the first level for the host, and we add 1 to go to the next + * level (which uses contatenation) for the stage-2 tables. + */ +#if PTRS_PER_S2_PGD <= 16 +#define KVM_PREALLOC_LEVEL (4 - CONFIG_ARM64_PGTABLE_LEVELS + 1) +#else +#define KVM_PREALLOC_LEVEL (0) +#endif + +/** + * kvm_prealloc_hwpgd - allocate inital table for VTTBR + * @kvm: The KVM struct pointer for the VM. + * @pgd: The kernel pseudo pgd + * + * When the kernel uses more levels of page tables than the guest, we allocate + * a fake PGD and pre-populate it to point to the next-level page table, which + * will be the real initial page table pointed to by the VTTBR. + * + * When KVM_PREALLOC_LEVEL==2, we allocate a single page for the PMD and + * the kernel will use folded pud. When KVM_PREALLOC_LEVEL==1, we + * allocate 2 consecutive PUD pages. + */ +static inline int kvm_prealloc_hwpgd(struct kvm *kvm, pgd_t *pgd) +{ + pud_t *pud; + pmd_t *pmd; + unsigned int order, i; + unsigned long hwpgd; + + if (KVM_PREALLOC_LEVEL == 0) + return 0; + + order = get_order(PTRS_PER_S2_PGD); + hwpgd = __get_free_pages(GFP_KERNEL | __GFP_ZERO, order); + if (!hwpgd) + return -ENOMEM; + + if (KVM_PREALLOC_LEVEL == 1) { + pud = (pud_t *)hwpgd; + for (i = 0; i < PTRS_PER_S2_PGD; i++) + pgd_populate(NULL, pgd + i, pud + i * PTRS_PER_PUD); + } else if (KVM_PREALLOC_LEVEL == 2) { + pud = pud_offset(pgd, 0); + pmd = (pmd_t *)hwpgd; + for (i = 0; i < PTRS_PER_S2_PGD; i++) + pud_populate(NULL, pud + i, pmd + i * PTRS_PER_PMD); + } + + return 0; +} + +static inline void *kvm_get_hwpgd(struct kvm *kvm) +{ + pgd_t *pgd = kvm->arch.pgd; + pud_t *pud; + pmd_t *pmd; + + switch (KVM_PREALLOC_LEVEL) { + case 0: + return pgd; + case 1: + pud = pud_offset(pgd, 0); + return pud; + case 2: + pud = pud_offset(pgd, 0); + pmd = pmd_offset(pud, 0); + return pmd; + default: + BUG(); + return NULL; + } +} + +static inline void kvm_free_hwpgd(struct kvm *kvm) +{ + if (KVM_PREALLOC_LEVEL > 0) { + unsigned long hwpgd = (unsigned long)kvm_get_hwpgd(kvm); + free_pages(hwpgd, get_order(S2_PGD_ORDER)); + } +} struct kvm; Thanks, -Christoffer