motorhead/qemu
1
0
Fork 0
mirror of https://github.com/Motorhead1991/qemu.git synced 2025-08-03 07:43:54 -06:00
Code Issues Projects Releases Packages Wiki Activity Actions

i386/kvm: Prefault memory on page state change

Browse source 
A page state change is typically followed by an access of the page(s) and
results in another VMEXIT in order to map the page into the nested page
table. Depending on the size of page state change request, this can
generate a number of additional VMEXITs. For example, under SNP, when
Linux is utilizing lazy memory acceptance, memory is typically accepted in
4M chunks. A page state change request is submitted to mark the pages as
private, followed by validation of the memory. Since the guest_memfd
currently only supports 4K pages, each page validation will result in
VMEXIT to map the page, resulting in 1024 additional exits.

When performing a page state change, invoke KVM_PRE_FAULT_MEMORY for the
size of the page state change in order to pre-map the pages and avoid the
additional VMEXITs. This helps speed up boot times.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/f5411c42340bd2f5c14972551edb4e959995e42b.1743193824.git.thomas.lendacky@amd.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Tom Lendacky 2025-03-28 15:30:24 -05:00 • committed by Paolo Bonzini
parent bc2a48d647
commit 4cdc489eb9
3 changed files with 29 additions and 5 deletions
Download patch file Download diff file Expand all files Collapse all files

1
include/system/kvm.h
View file

@ -42,6 +42,7 @@ extern bool kvm_gsi_routing_allowed;
extern bool kvm_gsi_direct_mapping;
extern bool kvm_readonly_mem_allowed;
extern bool kvm_msi_use_devid;
extern bool kvm_pre_fault_memory_supported;
#define kvm_enabled() (kvm_allowed)
/**