linux-kernel - [PATCH 5.12 507/677] powerpc/pseries: Add key to flags in pSeries_lpar_hpte

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Date:   Wed, 12 May 2021 16:49:13 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Michael Ellerman <mpe@...erman.id.au>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.12 507/677] powerpc/pseries: Add key to flags in pSeries_lpar_hpte_updateboltedpp()

From: Michael Ellerman <mpe@...erman.id.au>

[ Upstream commit b56d55a5aa4aa9fc166595a7feb57f153ef7b555 ]

The flags argument to plpar_pte_protect() (aka. H_PROTECT), includes
the key in bits 9-13, but currently we always set those bits to zero.

In the past that hasn't been a problem because we always used key 0
for the kernel, and updateboltedpp() is only used for kernel mappings.

However since commit d94b827e89dc ("powerpc/book3s64/kuap: Use Key 3
for kernel mapping with hash translation") we are now inadvertently
changing the key (to zero) when we call plpar_pte_protect().

That hasn't broken anything because updateboltedpp() is only used for
STRICT_KERNEL_RWX, which is currently disabled on 64s due to other
bugs.

But we want to fix that, so first we need to pass the key correctly to
plpar_pte_protect(). We can't pass our newpp value directly in, we
have to convert it into the form expected by the hcall.

The hcall we're using here is H_PROTECT, which is specified in section
14.5.4.1.6 of LoPAPR v1.1.

It takes a `flags` parameter, and the description for flags says:

 * flags: AVPN, pp0, pp1, pp2, key0-key4, n, and for the CMO
   option: CMO Option flags as defined in Table 189‚

If you then go to the start of the parent section, 14.5.4.1, on page
405, it says:

Register Linkage (For hcall() tokens 0x04 - 0x18)
 * On Call
   * R3 function call token
   * R4 flags (see Table 178‚ “Page Frame Table Access flags field
     definition‚” on page 401)

Then you have to go to section 14.5.3, and on page 394 there is a list
of hcalls and their tokens (table 176), and there you can see that
H_PROTECT == 0x18.

Finally you can look at table 178, on page 401, where it specifies the
layout of the bits for the key:

 Bit     Function
 -----------------
 50-54 | key0-key4

Those are big-endian bit numbers, converting to normal bit numbers you
get bits 9-13, or 0x3e00.

In the kernel we have:

  #define HPTE_R_KEY_HI		ASM_CONST(0x3000000000000000)
  #define HPTE_R_KEY_LO		ASM_CONST(0x0000000000000e00)

So the LO bits of newpp are already in the right place, and the HI
bits need to be shifted down by 48.

Fixes: d94b827e89dc ("powerpc/book3s64/kuap: Use Key 3 for kernel mapping with hash translation")
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Link: https://lore.kernel.org/r/20210331003845.216246-2-mpe@ellerman.id.au
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/powerpc/platforms/pseries/lpar.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/platforms/pseries/lpar.c b/arch/powerpc/platforms/pseries/lpar.c
index 3805519a6469..cd38bd421f38 100644
--- a/arch/powerpc/platforms/pseries/lpar.c
+++ b/arch/powerpc/platforms/pseries/lpar.c
@@ -977,11 +977,13 @@ static void pSeries_lpar_hpte_updateboltedpp(unsigned long newpp,
 	slot = pSeries_lpar_hpte_find(vpn, psize, ssize);
 	BUG_ON(slot == -1);

-	flags = newpp & 7;
+	flags = newpp & (HPTE_R_PP | HPTE_R_N);
 	if (mmu_has_feature(MMU_FTR_KERNEL_RO))
 		/* Move pp0 into bit 8 (IBM 55) */
 		flags |= (newpp & HPTE_R_PP0) >> 55;

+	flags |= ((newpp & HPTE_R_KEY_HI) >> 48) | (newpp & HPTE_R_KEY_LO);
+
 	lpar_rc = plpar_pte_protect(flags, slot, 0);

 	BUG_ON(lpar_rc != H_SUCCESS);
-- 
2.30.2