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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Oliver OHalloran <oohall@gmail.com>,
        Michael Ellerman <mpe@ellerman.id.au>
Subject: [PATCH 4.20 33/50] powerpc/papr_scm: Use the correct bind address
Date:   Wed, 13 Feb 2019 19:38:38 +0100
Message-Id: <20190213183658.371944412@linuxfoundation.org>
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4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Oliver O'Halloran <oohall@gmail.com>

commit 5a3840a470c41ec0b85cd36ca80370330656b163 upstream.

When binding an SCM volume to a physical address the hypervisor has the
option to return early with a continue token with the expectation that
the guest will resume the bind operation until it completes. A quirk of
this interface is that the bind address will only be returned by the
first bind h-call and the subsequent calls will return
0xFFFF_FFFF_FFFF_FFFF for the bind address.

We currently do not save the address returned by the first h-call. As a
result we will use the junk address as the base of the bound region if
the hypervisor decides to split the bind across multiple h-calls. This
bug was found when testing with very large SCM volumes where the bind
process would take more time than they hypervisor's internal h-call time
limit would allow. This patch fixes the issue by saving the bind address
from the first call.

Cc: stable@vger.kernel.org
Fixes: b5beae5e224f ("powerpc/pseries: Add driver for PAPR SCM regions")
Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/powerpc/platforms/pseries/papr_scm.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/arch/powerpc/platforms/pseries/papr_scm.c
+++ b/arch/powerpc/platforms/pseries/papr_scm.c
@@ -43,6 +43,7 @@ static int drc_pmem_bind(struct papr_scm
 {
 	unsigned long ret[PLPAR_HCALL_BUFSIZE];
 	uint64_t rc, token;
+	uint64_t saved = 0;
 
 	/*
 	 * When the hypervisor cannot map all the requested memory in a single
@@ -56,6 +57,8 @@ static int drc_pmem_bind(struct papr_scm
 		rc = plpar_hcall(H_SCM_BIND_MEM, ret, p->drc_index, 0,
 				p->blocks, BIND_ANY_ADDR, token);
 		token = ret[0];
+		if (!saved)
+			saved = ret[1];
 		cond_resched();
 	} while (rc == H_BUSY);
 
@@ -64,7 +67,7 @@ static int drc_pmem_bind(struct papr_scm
 		return -ENXIO;
 	}
 
-	p->bound_addr = ret[1];
+	p->bound_addr = saved;
 
 	dev_dbg(&p->pdev->dev, "bound drc %x to %pR\n", p->drc_index, &p->res);