linux-kernel - Re: [PATCH -for-next] riscv: Fix missing PAGE_PFN

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Date:   Fri, 03 Jun 2022 16:59:17 +0200
From:   Heiko Stuebner <heiko@...ech.de>
To:     Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Anup Patel <anup@...infault.org>,
        Atish Patra <atishp@...shpatra.org>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, kvm-riscv@...ts.infradead.org
Cc:     Alexandre Ghiti <alexandre.ghiti@...onical.com>,
        Alexandre Ghiti <alexandre.ghiti@...onical.com>
Subject: Re: [PATCH -for-next] riscv: Fix missing PAGE_PFN_MASK

Hi,

Am Montag, 30. Mai 2022, 11:47:01 CEST schrieb Alexandre Ghiti:
> There are a bunch of functions that use the PFN from a page table entry
> that end up with the svpbmt upper-bits because they are missing the newly
> introduced PAGE_PFN_MASK which leads to wrong addresses conversions and
> then crash: fix this by adding this mask.
> 
> Fixes: 100631b48ded ("riscv: Fix accessing pfn bits in PTEs for non-32bit variants")
> Signed-off-by: Alexandre Ghiti <alexandre.ghiti@...onical.com>

agree with the approach but some things below:

> ---
>  arch/riscv/include/asm/pgtable-64.h | 4 ++--
>  arch/riscv/include/asm/pgtable.h    | 4 ++--
>  arch/riscv/kvm/mmu.c                | 2 +-
>  3 files changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/riscv/include/asm/pgtable-64.h b/arch/riscv/include/asm/pgtable-64.h
> index 6d59e4695200..0e57bf1e25e9 100644
> --- a/arch/riscv/include/asm/pgtable-64.h
> +++ b/arch/riscv/include/asm/pgtable-64.h
> @@ -153,7 +153,7 @@ static inline pud_t pfn_pud(unsigned long pfn, pgprot_t prot)
>  
>  static inline unsigned long _pud_pfn(pud_t pud)
>  {
> -	return pud_val(pud) >> _PAGE_PFN_SHIFT;
> +	return (pud_val(pud) & _PAGE_PFN_MASK) >> _PAGE_PFN_SHIFT;

we already have defined a helper:
	#define __page_val_to_pfn(_val)  (((_val) & _PAGE_PFN_MASK) >> _PAGE_PFN_SHIFT)

so maybe just use

	return __page_val_to_pfn(pud_val(pud));

>  }
>  
>  static inline pmd_t *pud_pgtable(pud_t pud)
> @@ -240,7 +240,7 @@ static inline void p4d_clear(p4d_t *p4d)
>  static inline pud_t *p4d_pgtable(p4d_t p4d)
>  {
>  	if (pgtable_l4_enabled)
> -		return (pud_t *)pfn_to_virt(p4d_val(p4d) >> _PAGE_PFN_SHIFT);
> +		return (pud_t *)pfn_to_virt((p4d_val(p4d) & _PAGE_PFN_MASK) >> _PAGE_PFN_SHIFT);

	return (pud_t *)pfn_to_virt(__page_val_to_pfn(p4d_val(p4d)));

>  
>  	return (pud_t *)pud_pgtable((pud_t) { p4d_val(p4d) });
>  }
> diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
> index e2658a25f06d..43064025f4b0 100644
> --- a/arch/riscv/include/asm/pgtable.h
> +++ b/arch/riscv/include/asm/pgtable.h
> @@ -255,7 +255,7 @@ static inline pgd_t pfn_pgd(unsigned long pfn, pgprot_t prot)
>  
>  static inline unsigned long _pgd_pfn(pgd_t pgd)
>  {
> -	return pgd_val(pgd) >> _PAGE_PFN_SHIFT;
> +	return (pgd_val(pgd) & _PAGE_PFN_MASK) >> _PAGE_PFN_SHIFT;

	return __page_val_to_pfn(pgd_val(pgd));

>  }
>  
>  static inline struct page *pmd_page(pmd_t pmd)
> @@ -568,7 +568,7 @@ static inline pmd_t pmd_mkinvalid(pmd_t pmd)
>  	return __pmd(pmd_val(pmd) & ~(_PAGE_PRESENT|_PAGE_PROT_NONE));
>  }
>  
> -#define __pmd_to_phys(pmd)  (pmd_val(pmd) >> _PAGE_PFN_SHIFT << PAGE_SHIFT)
> +#define __pmd_to_phys(pmd)  ((pmd_val(pmd) & _PAGE_PFN_MASK) >> _PAGE_PFN_SHIFT << PAGE_SHIFT)

	#define __pmd_to_phys(pmd)  (__page_val_to_pfn(pmd_val(pmd)) << PAGE_SHIFT)

>  
>  static inline unsigned long pmd_pfn(pmd_t pmd)
>  {
> diff --git a/arch/riscv/kvm/mmu.c b/arch/riscv/kvm/mmu.c
> index f80a34fbf102..db03c5a29d4c 100644
> --- a/arch/riscv/kvm/mmu.c
> +++ b/arch/riscv/kvm/mmu.c
> @@ -55,7 +55,7 @@ static inline unsigned long stage2_pte_index(gpa_t addr, u32 level)
>  
>  static inline unsigned long stage2_pte_page_vaddr(pte_t pte)

This got renamed to gstage_pte_page_vaddr()
in commit 26708234eb12 ("RISC-V: KVM: Use G-stage name for hypervisor page table")

>  {
> -	return (unsigned long)pfn_to_virt(pte_val(pte) >> _PAGE_PFN_SHIFT);
> +	return (unsigned long)pfn_to_virt((pte_val(pte) & _PAGE_PFN_MASK) >> _PAGE_PFN_SHIFT);

return (unsigned long)pfn_to_virt(__page_val_to_pfn(pte_val(pte)));


Heiko

>  }
>  
>  static int stage2_page_size_to_level(unsigned long page_size, u32 *out_level)
>