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KVM: x86/mmu: Clean up function comments for dirty logging APIs

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Rework the function comment for kvm_arch_mmu_enable_log_dirty_pt_masked()
into the body of the function, as it has gotten a bit stale, is harder to
read without the code context, and is the last source of warnings for W=1
builds in KVM x86 due to using a kernel-doc comment without documenting
all parameters.

Opportunistically subsume the functions comments for
kvm_mmu_write_protect_pt_masked() and kvm_mmu_clear_dirty_pt_masked(), as
there is no value in regurgitating similar information at a higher level,
and capturing the differences between write-protection and PML-based dirty
logging is best done in a common location.

No functional change intended.

Cc: David Matlack <dmatlack@google.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Pankaj Gupta <pankaj.gupta@amd.com>
Link: https://lore.kernel.org/r/20240802202006.340854-1-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson
2024-08-02 13:20:06 -07:00
parent 47ac09b91b
commit acf2923271
1 changed files with 15 additions and 33 deletions
Download Patch File Download Diff File Expand all files Collapse all files

48
arch/x86/kvm/mmu/mmu.c
View File

@@ -1307,15 +1307,6 @@ static bool __rmap_clear_dirty(struct kvm *kvm, struct kvm_rmap_head *rmap_head,
return flush;
}
/**
* kvm_mmu_write_protect_pt_masked - write protect selected PT level pages
* @kvm: kvm instance
* @slot: slot to protect
* @gfn_offset: start of the BITS_PER_LONG pages we care about
* @mask: indicates which pages we should protect
*
* Used when we do not need to care about huge page mappings.
*/
static void kvm_mmu_write_protect_pt_masked(struct kvm *kvm,
struct kvm_memory_slot *slot,
gfn_t gfn_offset, unsigned long mask)
@@ -1339,16 +1330,6 @@ static void kvm_mmu_write_protect_pt_masked(struct kvm *kvm,
}
}
/**
* kvm_mmu_clear_dirty_pt_masked - clear MMU D-bit for PT level pages, or write
* protect the page if the D-bit isn't supported.
* @kvm: kvm instance
* @slot: slot to clear D-bit
* @gfn_offset: start of the BITS_PER_LONG pages we care about
* @mask: indicates which pages we should clear D-bit
*
* Used for PML to re-log the dirty GPAs after userspace querying dirty_bitmap.
*/
static void kvm_mmu_clear_dirty_pt_masked(struct kvm *kvm,
struct kvm_memory_slot *slot,
gfn_t gfn_offset, unsigned long mask)
@@ -1372,24 +1353,16 @@ static void kvm_mmu_clear_dirty_pt_masked(struct kvm *kvm,
}
}
/**
* kvm_arch_mmu_enable_log_dirty_pt_masked - enable dirty logging for selected
* PT level pages.
*
* It calls kvm_mmu_write_protect_pt_masked to write protect selected pages to
* enable dirty logging for them.
*
* We need to care about huge page mappings: e.g. during dirty logging we may
* have such mappings.
*/
void kvm_arch_mmu_enable_log_dirty_pt_masked(struct kvm *kvm,
struct kvm_memory_slot *slot,
gfn_t gfn_offset, unsigned long mask)
{
/*
* Huge pages are NOT write protected when we start dirty logging in
* initially-all-set mode; must write protect them here so that they
* are split to 4K on the first write.
* If the slot was assumed to be "initially all dirty", write-protect
* huge pages to ensure they are split to 4KiB on the first write (KVM
* dirty logs at 4KiB granularity). If eager page splitting is enabled,
* immediately try to split huge pages, e.g. so that vCPUs don't get
* saddled with the cost of splitting.
*
* The gfn_offset is guaranteed to be aligned to 64, but the base_gfn
* of memslot has no such restriction, so the range can cross two large
@@ -1411,7 +1384,16 @@ void kvm_arch_mmu_enable_log_dirty_pt_masked(struct kvm *kvm,
PG_LEVEL_2M);
}
/* Now handle 4K PTEs. */
/*
* (Re)Enable dirty logging for all 4KiB SPTEs that map the GFNs in
* mask. If PML is enabled and the GFN doesn't need to be write-
* protected for other reasons, e.g. shadow paging, clear the Dirty bit.
* Otherwise clear the Writable bit.
*
* Note that kvm_mmu_clear_dirty_pt_masked() is called whenever PML is
* enabled but it chooses between clearing the Dirty bit and Writeable
* bit based on the context.
*/
if (kvm_x86_ops.cpu_dirty_log_size)
kvm_mmu_clear_dirty_pt_masked(kvm, slot, gfn_offset, mask);
else