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Message-ID: <ZYGCcxhGuXlP4mbY@google.com>
Date: Tue, 19 Dec 2023 11:45:55 +0000
From: Sebastian Ene <sebastianene@...gle.com>
To: will@...nel.org, Oliver Upton <oliver.upton@...ux.dev>,
James Morse <james.morse@....com>,
Suzuki K Poulose <suzuki.poulose@....com>,
Zenghui Yu <yuzenghui@...wei.com>, catalin.marinas@....com,
mark.rutland@....com, akpm@...ux-foundation.org, maz@...nel.org
Cc: kvmarm@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
linux-kernel@...r.kernel.org, kernel-team@...roid.com,
vdonnefort@...gle.com, qperret@...gle.com, smostafa@...gle.com
Subject: Re: [PATCH v4 03/10] KVM: arm64: Invoke the snapshot interface for
the host stage-2 pagetable
On Mon, Dec 18, 2023 at 01:58:53PM +0000, Sebastian Ene wrote:
> Allocate memory for the snapshot by creating a memory cache with empty
> pages that will be used by the hypervisor during the page table copy.
> Get the required size of the PGD and allocate physically contiguous
> memory for it. Allocate contiguous memory for an array that is used to
> keep track of the pages used from the memcache. Call the snapshot
> interface and release the memory for the snapshot.
>
> Signed-off-by: Sebastian Ene <sebastianene@...gle.com>
> ---
> arch/arm64/kvm/ptdump.c | 107 ++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 107 insertions(+)
>
> diff --git a/arch/arm64/kvm/ptdump.c b/arch/arm64/kvm/ptdump.c
> index 5816fc632..e99bab427 100644
> --- a/arch/arm64/kvm/ptdump.c
> +++ b/arch/arm64/kvm/ptdump.c
> @@ -25,6 +25,9 @@ static int kvm_ptdump_open(struct inode *inode, struct file *file);
> static int kvm_ptdump_release(struct inode *inode, struct file *file);
> static int kvm_ptdump_show(struct seq_file *m, void *);
>
> +static phys_addr_t get_host_pa(void *addr);
> +static void *get_host_va(phys_addr_t pa);
> +
> static const struct file_operations kvm_ptdump_fops = {
> .open = kvm_ptdump_open,
> .read = seq_read,
> @@ -32,6 +35,11 @@ static const struct file_operations kvm_ptdump_fops = {
> .release = kvm_ptdump_release,
> };
>
> +static struct kvm_pgtable_mm_ops ptdump_host_mmops = {
> + .phys_to_virt = get_host_va,
> + .virt_to_phys = get_host_pa,
> +};
> +
> static int kvm_ptdump_open(struct inode *inode, struct file *file)
> {
> struct kvm_ptdump_register *reg = inode->i_private;
> @@ -78,11 +86,110 @@ static void kvm_ptdump_debugfs_register(struct kvm_ptdump_register *reg,
>
> static struct kvm_ptdump_register host_reg;
>
> +static size_t host_stage2_get_pgd_len(void)
> +{
> + u32 phys_shift = get_kvm_ipa_limit();
> + u64 vtcr = kvm_get_vtcr(read_sanitised_ftr_reg(SYS_ID_AA64MMFR0_EL1),
> + read_sanitised_ftr_reg(SYS_ID_AA64MMFR1_EL1),
> + phys_shift);
> + return (kvm_pgtable_stage2_pgd_size(vtcr) >> PAGE_SHIFT);
> +}
> +
> +static phys_addr_t get_host_pa(void *addr)
> +{
> + return __pa(addr);
> +}
> +
> +static void *get_host_va(phys_addr_t pa)
> +{
> + return __va(pa);
> +}
> +
> +static void kvm_host_put_ptdump_info(void *snap)
> +{
> + void *mc_page;
> + size_t i;
> + struct kvm_pgtable_snapshot *snapshot;
> +
> + if (!snap)
> + return;
> +
> + snapshot = snap;
> + while ((mc_page = pop_hyp_memcache(&snapshot->mc, get_host_va)) != NULL)
> + free_page((unsigned long)mc_page);
> +
> + if (snapshot->pgd_hva)
> + free_pages_exact(snapshot->pgd_hva, snapshot->pgd_pages);
> +
> + if (snapshot->used_pages_hva) {
> + for (i = 0; i < snapshot->used_pages_indx; i++) {
> + mc_page = get_host_va(snapshot->used_pages_hva[i]);
> + free_page((unsigned long)mc_page);
> + }
> +
> + free_pages_exact(snapshot->used_pages_hva, snapshot->num_used_pages);
> + }
> +
> + free_page((unsigned long)snapshot);
> +}
> +
> +static void *kvm_host_get_ptdump_info(struct kvm_ptdump_register *reg)
> +{
> + int i, ret;
> + void *mc_page;
> + struct kvm_pgtable_snapshot *snapshot;
> + size_t memcache_len;
> +
> + snapshot = (void *)__get_free_page(GFP_KERNEL_ACCOUNT);
> + if (!snapshot)
> + return NULL;
> +
> + memset(snapshot, 0, sizeof(struct kvm_pgtable_snapshot));
> +
> + snapshot->pgd_pages = host_stage2_get_pgd_len();
> + snapshot->pgd_hva = alloc_pages_exact(snapshot->pgd_pages, GFP_KERNEL_ACCOUNT);
The allocation should be specified in the number of bytes here.
> + if (!snapshot->pgd_hva)
> + goto err;
> +
> + memcache_len = (size_t)reg->priv;
> + for (i = 0; i < memcache_len; i++) {
> + mc_page = (void *)__get_free_page(GFP_KERNEL_ACCOUNT);
> + if (!mc_page)
> + goto err;
> +
> + push_hyp_memcache(&snapshot->mc, mc_page, get_host_pa);
> + }
> +
> + snapshot->num_used_pages = DIV_ROUND_UP(sizeof(phys_addr_t) * memcache_len,
> + PAGE_SIZE);
> + snapshot->used_pages_hva = alloc_pages_exact(snapshot->num_used_pages,
> + GFP_KERNEL_ACCOUNT);
the same as previous comment.
> + if (!snapshot->used_pages_hva)
> + goto err;
> +
> + ret = kvm_call_hyp_nvhe(__pkvm_host_stage2_snapshot, snapshot);
> + if (ret) {
> + pr_err("ERROR %d snapshot host pagetables\n", ret);
> + goto err;
> + }
> +
> + snapshot->pgtable.pgd = get_host_va((phys_addr_t)snapshot->pgtable.pgd);
> + snapshot->pgtable.mm_ops = &ptdump_host_mmops;
> +
> + return snapshot;
> +err:
> + kvm_host_put_ptdump_info(snapshot);
> + return NULL;
> +}
> +
> void kvm_ptdump_register_host(void)
> {
> if (!is_protected_kvm_enabled())
> return;
>
> + host_reg.get_ptdump_info = kvm_host_get_ptdump_info;
> + host_reg.put_ptdump_info = kvm_host_put_ptdump_info;
> +
> kvm_ptdump_debugfs_register(&host_reg, "host_page_tables",
> kvm_debugfs_dir);
> }
> --
> 2.43.0.472.g3155946c3a-goog
>
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