Re: [kvm-unit-tests PATCH v4 5/8] x86: nSVM: Build up the nested page table dynamically

[Sean Christopherson <seanjc@google.com>]

On Thu, Apr 28, 2022, Manali Shukla wrote:
> Current implementation of nested page table does the page table build
> up statistically with 2048 PTEs and one pml4 entry.
> That is why current implementation is not extensible.
> 
> New implementation does page table build up dynamically based on the
> RAM size of the VM which enables us to have separate memory range to
> test various npt test cases.

I'm guessing you know the drill :-)

> Signed-off-by: Manali Shukla <manali.shukla@amd.com>
> ---
>  x86/svm.c     | 75 ++++++++++++++++-----------------------------------
>  x86/svm.h     |  4 ++-
>  x86/svm_npt.c |  5 ++--
>  3 files changed, 29 insertions(+), 55 deletions(-)
> 
> diff --git a/x86/svm.c b/x86/svm.c
> index ec825c7..e66c801 100644
> --- a/x86/svm.c
> +++ b/x86/svm.c
> @@ -8,6 +8,7 @@
>  #include "desc.h"
>  #include "msr.h"
>  #include "vm.h"
> +#include "fwcfg.h"
>  #include "smp.h"
>  #include "types.h"
>  #include "alloc_page.h"
> @@ -16,43 +17,32 @@
>  #include "vmalloc.h"
>  
>  /* for the nested page table*/
> -u64 *pte[2048];
> -u64 *pde[4];
> -u64 *pdpe;
>  u64 *pml4e;
>  
>  struct vmcb *vmcb;
>  
>  u64 *npt_get_pte(u64 address)
>  {
> -	int i1, i2;
> -
> -	address >>= 12;
> -	i1 = (address >> 9) & 0x7ff;
> -	i2 = address & 0x1ff;
> -
> -	return &pte[i1][i2];
> +        return get_pte(npt_get_pml4e(), (void*)address);
>  }
>  
>  u64 *npt_get_pde(u64 address)
>  {
> -	int i1, i2;
> -
> -	address >>= 21;
> -	i1 = (address >> 9) & 0x3;
> -	i2 = address & 0x1ff;
> -
> -	return &pde[i1][i2];
> +    struct pte_search search;
> +    search = find_pte_level(npt_get_pml4e(), (void*)address, 2);
> +    return search.pte;
>  }
>  
> -u64 *npt_get_pdpe(void)
> +u64 *npt_get_pdpe(u64 address)
>  {
> -	return pdpe;
> +    struct pte_search search;
> +    search = find_pte_level(npt_get_pml4e(), (void*)address, 3);
> +    return search.pte;
>  }
>  
>  u64 *npt_get_pml4e(void)
>  {
> -	return pml4e;
> +    return pml4e;
>  }
>  
>  bool smp_supported(void)
> @@ -300,11 +290,21 @@ static void set_additional_vcpu_msr(void *msr_efer)
>  	wrmsr(MSR_EFER, (ulong)msr_efer | EFER_SVME);
>  }
>  
> +void setup_npt(void) {

Function braces go on a new line.

> +    u64 end_of_memory;
> +    pml4e = alloc_page();
> +

...

> diff --git a/x86/svm_npt.c b/x86/svm_npt.c
> index 53e8a90..ab4dcf4 100644
> --- a/x86/svm_npt.c
> +++ b/x86/svm_npt.c
> @@ -209,7 +209,8 @@ static void __svm_npt_rsvd_bits_test(u64 * pxe, u64 rsvd_bits, u64 efer,
>  	       "Wanted #NPF on rsvd bits = 0x%lx, got exit = 0x%x", rsvd_bits,
>  	       exit_reason);
>  
> -	if (pxe == npt_get_pdpe() || pxe == npt_get_pml4e()) {
> +	if (pxe == npt_get_pdpe((u64) basic_guest_main)
> +	    || pxe == npt_get_pml4e()) {

The "||" should be on the previous line.

>  		/*
>  		 * The guest's page tables will blow up on a bad PDPE/PML4E,
>  		 * before starting the final walk of the guest page.
> @@ -338,7 +339,7 @@ skip_pte_test:
>  				get_random_bits(20, 13) | PT_PAGE_SIZE_MASK,
>  				host_efer, host_cr4, guest_efer, guest_cr4);
>  
> -	_svm_npt_rsvd_bits_test(npt_get_pdpe(),
> +	_svm_npt_rsvd_bits_test(npt_get_pdpe((u64) basic_guest_main),
>  				PT_PAGE_SIZE_MASK |
>  				(this_cpu_has(X86_FEATURE_GBPAGES) ?
>  				 get_random_bits(29, 13) : 0), host_efer,
> -- 
> 2.30.2
>