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Message-ID: <ea30058d-f3e1-4a1f-bdcf-fafc92b221a0@kernel.org>
Date: Tue, 16 Dec 2025 08:08:07 -0600
From: Mario Limonciello <superm1@...nel.org>
To: "Lazar, Lijo" <lijo.lazar@....com>,
"Yo-Jung Leo Lin (AMD)" <Leo.Lin@....com>,
Alex Deucher <alexander.deucher@....com>,
Christian König <christian.koenig@....com>,
David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
Jonathan Corbet <corbet@....net>
Cc: amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
"Tsao, Anson" <anson.tsao@....com>
Subject: Re: [PATCH v6 4/5] drm/amdgpu: add UMA allocation interfaces to sysfs
On 12/16/25 3:43 AM, Lazar, Lijo wrote:
>
>
> On 12-Dec-25 1:29 PM, Yo-Jung Leo Lin (AMD) wrote:
>> Add a uma/ directory containing two sysfs files as interfaces to
>> inspect or change UMA carveout size. These files are:
>>
>> - uma/carveout_options: a read-only file listing all the available
>> UMA allocation options and their index.
>>
>> - uma/carveout: a file that is both readable and writable. On read,
>> it shows the index of the current setting. Writing a valid index
>> into this file allows users to change the UMA carveout size to that
>> option on the next boot.
>>
>> Co-developed-by: Mario Limonciello (AMD) <superm1@...nel.org>
>> Signed-off-by: Mario Limonciello (AMD) <superm1@...nel.org>
>> Reviewed-by: Alex Deucher <alexander.deucher@....com>
>> Signed-off-by: Yo-Jung Leo Lin (AMD) <Leo.Lin@....com>
>> ---
>> drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 143 +++++++++++++++++++
>> ++++++++++
>> 1 file changed, 143 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/
>> drm/amd/amdgpu/amdgpu_device.c
>> index 903c4706040d..e78e6982312c 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>> @@ -36,6 +36,7 @@
>> #include <linux/pci.h>
>> #include <linux/pci-p2pdma.h>
>> #include <linux/apple-gmux.h>
>> +#include <linux/nospec.h>
>> #include <drm/drm_atomic_helper.h>
>> #include <drm/drm_client_event.h>
>> @@ -417,6 +418,146 @@ static const struct attribute_group
>> amdgpu_board_attrs_group = {
>> .is_visible = amdgpu_board_attrs_is_visible
>> };
>> +static ssize_t carveout_options_show(struct device *dev,
>> + struct device_attribute *attr,
>> + char *buf)
>> +{
>> + struct drm_device *ddev = dev_get_drvdata(dev);
>> + struct amdgpu_device *adev = drm_to_adev(ddev);
>> + struct amdgpu_uma_carveout_info *uma_info = &adev->uma_info;
>> + uint32_t memory_carved;
>> + ssize_t size = 0;
>> +
>> + if (!uma_info || !uma_info->num_entries)
>> + return -ENODEV;
>> +
>> + for (int i = 0; i < uma_info->num_entries; i++) {
>> + memory_carved = uma_info->entries[i].memory_carved_mb;
>> + if (memory_carved >= SZ_1G/SZ_1M) {
>> + size += sysfs_emit_at(buf, size, "%d: %s (%u GB)\n",
>> + i,
>> + uma_info->entries[i].name,
>> + memory_carved >> 10);
>> + } else {
>> + size += sysfs_emit_at(buf, size, "%d: %s (%u MB)\n",
>> + i,
>> + uma_info->entries[i].name,
>> + memory_carved);
>> + }
>> + }
>> +
>> + return size;
>> +}
>> +static DEVICE_ATTR_RO(carveout_options);
>> +
>> +static ssize_t carveout_show(struct device *dev,
>> + struct device_attribute *attr,
>> + char *buf)
>> +{
>> + struct drm_device *ddev = dev_get_drvdata(dev);
>> + struct amdgpu_device *adev = drm_to_adev(ddev);
>> +
>> + return sysfs_emit(buf, "%u\n", adev->uma_info.uma_option_index);
>
> It would be better to show the size along with the index.
This idea complicates userspace parsing because rather than a atoi()
parser you now need to do sscanf().
IE - I like it the way it is in the series at the moment.
>
> Regardless, series is -
>
> Reviewed-by: Lijo Lazar <lijo.lazar@....com>
>
> Thanks,
> Lijo
>
>> +}
>> +
>> +static ssize_t carveout_store(struct device *dev,
>> + struct device_attribute *attr,
>> + const char *buf, size_t count)
>> +{
>> + struct drm_device *ddev = dev_get_drvdata(dev);
>> + struct amdgpu_device *adev = drm_to_adev(ddev);
>> + struct amdgpu_uma_carveout_info *uma_info = &adev->uma_info;
>> + struct amdgpu_uma_carveout_option *opt;
>> + unsigned long val;
>> + uint8_t flags;
>> + int r;
>> +
>> + r = kstrtoul(buf, 10, &val);
>> + if (r)
>> + return r;
>> +
>> + if (val >= uma_info->num_entries)
>> + return -EINVAL;
>> +
>> + val = array_index_nospec(val, uma_info->num_entries);
>> + opt = &uma_info->entries[val];
>> +
>> + if (!(opt->flags & AMDGPU_UMA_FLAG_AUTO) &&
>> + !(opt->flags & AMDGPU_UMA_FLAG_CUSTOM)) {
>> + drm_err_once(ddev, "Option %lu not supported due to lack of
>> Custom/Auto flag", val);
>> + return -EINVAL;
>> + }
>> +
>> + flags = opt->flags;
>> + flags &= ~((flags & AMDGPU_UMA_FLAG_AUTO) >> 1);
>> +
>> + guard(mutex)(&uma_info->update_lock);
>> +
>> + r = amdgpu_acpi_set_uma_allocation_size(adev, val, flags);
>> + if (r)
>> + return r;
>> +
>> + uma_info->uma_option_index = val;
>> +
>> + return count;
>> +}
>> +static DEVICE_ATTR_RW(carveout);
>> +
>> +static struct attribute *amdgpu_uma_attrs[] = {
>> + &dev_attr_carveout.attr,
>> + &dev_attr_carveout_options.attr,
>> + NULL
>> +};
>> +
>> +const struct attribute_group amdgpu_uma_attr_group = {
>> + .name = "uma",
>> + .attrs = amdgpu_uma_attrs
>> +};
>> +
>> +static void amdgpu_uma_sysfs_init(struct amdgpu_device *adev)
>> +{
>> + int rc;
>> +
>> + if (!(adev->flags & AMD_IS_APU))
>> + return;
>> +
>> + if (!amdgpu_acpi_is_set_uma_allocation_size_supported())
>> + return;
>> +
>> + rc = amdgpu_atomfirmware_get_uma_carveout_info(adev, &adev-
>> >uma_info);
>> + if (rc) {
>> + drm_dbg(adev_to_drm(adev),
>> + "Failed to parse UMA carveout info from VBIOS: %d\n", rc);
>> + goto out_info;
>> + }
>> +
>> + mutex_init(&adev->uma_info.update_lock);
>> +
>> + rc = devm_device_add_group(adev->dev, &amdgpu_uma_attr_group);
>> + if (rc) {
>> + drm_dbg(adev_to_drm(adev), "Failed to add UMA carveout sysfs
>> interfaces %d\n", rc);
>> + goto out_attr;
>> + }
>> +
>> + return;
>> +
>> +out_attr:
>> + mutex_destroy(&adev->uma_info.update_lock);
>> +out_info:
>> + return;
>> +}
>> +
>> +static void amdgpu_uma_sysfs_fini(struct amdgpu_device *adev)
>> +{
>> + struct amdgpu_uma_carveout_info *uma_info = &adev->uma_info;
>> +
>> + if (!amdgpu_acpi_is_set_uma_allocation_size_supported())
>> + return;
>> +
>> + mutex_destroy(&uma_info->update_lock);
>> + uma_info->num_entries = 0;
>> +}
>> +
>> static void amdgpu_device_get_pcie_info(struct amdgpu_device *adev);
>> /**
>> @@ -4492,6 +4633,7 @@ static int
>> amdgpu_device_sys_interface_init(struct amdgpu_device *adev)
>> amdgpu_fru_sysfs_init(adev);
>> amdgpu_reg_state_sysfs_init(adev);
>> amdgpu_xcp_sysfs_init(adev);
>> + amdgpu_uma_sysfs_init(adev);
>> return r;
>> }
>> @@ -4507,6 +4649,7 @@ static void
>> amdgpu_device_sys_interface_fini(struct amdgpu_device *adev)
>> amdgpu_reg_state_sysfs_fini(adev);
>> amdgpu_xcp_sysfs_fini(adev);
>> + amdgpu_uma_sysfs_fini(adev);
>> }
>> /**
>>
>
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