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From:   "M. Vefa Bicakci" <m.v.b@runbox.com>
To:     platform-driver-x86@vger.kernel.org, linux-kernel@vger.kernel.org
Cc:     Rajneesh Bhardwaj <rajneesh.bhardwaj@intel.com>,
        Vishwanath Somayaji <vishwanath.somayaji@intel.com>,
        Darren Hart <dvhart@infradead.org>,
        Andy Shevchenko <andy@infradead.org>,
        "M. Vefa Bicakci" <m.v.b@runbox.com>
Subject: [PATCH] platform/x86: intel_pmc_core: Do not ioremap RAM
Date:   Thu, 15 Aug 2019 21:41:39 -0400
Message-Id: <20190816014140.10687-1-m.v.b@runbox.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On a Xen-based PVH virtual machine with more than 4 GiB of RAM,
intel_pmc_core fails initialization with the following warning message
from the kernel, indicating that the driver is attempting to ioremap
RAM:

  ------------[ cut here ]------------
  ioremap on RAM at 0x00000000fe000000 - 0x00000000fe001fff
  WARNING: CPU: 1 PID: 434 at arch/x86/mm/ioremap.c:186 __ioremap_caller.constprop.0+0x2aa/0x2c0
  Modules linked in: intel_pmc_core_pltdrv(+) xen_netfront(+) intel_pmc_core \
    crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel \
    intel_rapl_perf pcspkr binfmt_misc u2mfn(O) xenfs xen_gntdev \
    xen_gntalloc xen_blkback xen_privcmd xen_evtchn ip_tables overlay \
    xen_blkfront
  CPU: 1 PID: 434 Comm: systemd-udevd Tainted: G           O      5.3.0-rc3-next-20190809-1 #2
  RIP: 0010:__ioremap_caller.constprop.0+0x2aa/0x2c0
  Code: 05 0f c9 1b 01 49 09 c6 e9 8e fe ff ff 48 8d 54 24 28 48 c7 c7 68 87 0a 82 c6 05 c4 23 2b 01 01 48 8d 74 24 18 e8 d4 4a 06 00 <0f> 0b 45 31 ff e9 fe fe ff ff e8 e7 47 06 00 0f 1f 80 00 00 00 00
  RSP: 0018:ffffc900002dfa20 EFLAGS: 00010282
  RAX: 0000000000000000 RBX: ffffffffc0107000 RCX: 0000000000000006
  RDX: 0000000000000007 RSI: 0000000000000092 RDI: ffff88813bb17540
  RBP: 00000000fe000000 R08: 000000000000015f R09: 000000000000000a
  R10: 000000000000000a R11: ffffc900002df8da R12: 0000000000002000
  R13: 0000000000000000 R14: 0000000000000002 R15: ffffffff822da3a0
  FS:  000072ecce666940(0000) GS:ffff88813bb00000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 0000785be7346d20 CR3: 000000000d872001 CR4: 00000000003606e0
  Call Trace:
   ? pmc_core_probe+0x87/0x2d0 [intel_pmc_core]
   pmc_core_probe+0x87/0x2d0 [intel_pmc_core]
   platform_drv_probe+0x35/0x80
   really_probe+0x298/0x3c0
   driver_probe_device+0x7a/0x100
   ? driver_allows_async_probing+0x50/0x50
   bus_for_each_drv+0x8f/0xd0
   __device_attach+0xf0/0x170
   bus_probe_device+0x8e/0xa0
   device_add+0x692/0x7e0
   platform_device_add+0xe9/0x240
   ? 0xffffffffc00ec000
   do_one_initcall+0x59/0x214
   do_init_module+0x5c/0x230
   load_module+0x258d/0x2840
   ? __do_sys_finit_module+0xbb/0x120
   __do_sys_finit_module+0xbb/0x120
   do_syscall_64+0x5f/0x1a0
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x72eccf662fad
  Code: 00 c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d ab 9e 0c 00 f7 d8 64 89 01 48
  RSP: 002b:00007ffd3710d018 EFLAGS: 00000246 ORIG_RAX: 0000000000000139
  RAX: ffffffffffffffda RBX: 000060ab8fda2530 RCX: 000072eccf662fad
  RDX: 0000000000000000 RSI: 000072eccf2bd84d RDI: 0000000000000017
  RBP: 0000000000020000 R08: 0000000000000000 R09: 0000000000000007
  R10: 0000000000000017 R11: 0000000000000246 R12: 000072eccf2bd84d
  R13: 0000000000000000 R14: 000060ab8fd9b5e0 R15: 0000000000000007
  ---[ end trace 5e5421608729d6f4 ]---

This issue appears to manifest itself because of the following fallback
mechanism in the driver:

	if (lpit_read_residency_count_address(&slp_s0_addr))
		pmcdev->base_addr = PMC_BASE_ADDR_DEFAULT;

The validity of address PMC_BASE_ADDR_DEFAULT (i.e., 0xFE000000) is not
verified by the driver, which is what this patch introduces. With this
patch, if address PMC_BASE_ADDR_DEFAULT is in RAM, then the driver will
not attempt to ioremap the aforementioned address.

Signed-off-by: M. Vefa Bicakci <m.v.b@runbox.com>
---
 drivers/platform/x86/intel_pmc_core.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/platform/x86/intel_pmc_core.c b/drivers/platform/x86/intel_pmc_core.c
index c510d0d72475..3b6b8dcc4767 100644
--- a/drivers/platform/x86/intel_pmc_core.c
+++ b/drivers/platform/x86/intel_pmc_core.c
@@ -878,10 +878,14 @@ static int pmc_core_probe(struct platform_device *pdev)
 	if (pmcdev->map == &spt_reg_map && !pci_dev_present(pmc_pci_ids))
 		pmcdev->map = &cnp_reg_map;
 
-	if (lpit_read_residency_count_address(&slp_s0_addr))
+	if (lpit_read_residency_count_address(&slp_s0_addr)) {
 		pmcdev->base_addr = PMC_BASE_ADDR_DEFAULT;
-	else
+
+		if (page_is_ram(PHYS_PFN(pmcdev->base_addr)))
+			return -ENODEV;
+	} else {
 		pmcdev->base_addr = slp_s0_addr - pmcdev->map->slp_s0_offset;
+	}
 
 	pmcdev->regbase = ioremap(pmcdev->base_addr,
 				  pmcdev->map->regmap_length);
-- 
2.21.0